libdtrace/common/dt_aggregate.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright (c) 2003, 2012, Oracle and/or its affiliates. All rights reserved.
 */

#include <stdlib.h>
#include <strings.h>
#include <errno.h>
#include <unistd.h>
#include <dt_impl.h>
#include <assert.h>
#include <alloca.h>
#include <limits.h>

static size_t dtrace_ahashsize[] = {
    32779,
    500009,
    2104987,
    4000037,
    7954979
    };

#define DTRACE_NUM_AHASHSIZE    \
    (sizeof (dtrace_ahashsize) / sizeof (dtrace_ahashsize[0]))

#define LSHIFT 4
#define RSHIFT (sizeof (caddr_t) * 8 - LSHIFT)
/*
 * Rotate the hash by LSHIFT bits, then XOR the next word.
 * hashval must be an unsigned type.
 */
#define DTRACE_AGG_HASH(hashval, addr, roffs) \
    {                             \
        hashval = (hashval << LSHIFT) | (hashval >> RSHIFT); \
        hashval = hashval ^ ((unsigned long) addr[roffs]);   \
    }

/*
 * Because qsort(3C) does not allow an argument to be passed to a comparison
 * function, the variables that affect comparison must regrettably be global;
 * they are protected by a global static lock, dt_qsort_lock.
 */
static pthread_mutex_t dt_qsort_lock = PTHREAD_MUTEX_INITIALIZER;

static int dt_revsort;
static int dt_keysort;
static int dt_keypos;

#define DT_LESSTHAN (dt_revsort == 0 ? -1 : 1)
#define DT_GREATERTHAN  (dt_revsort == 0 ? 1 : -1)

static void
dt_aggregate_count(int64_t *existing, int64_t *new, size_t size)
{
    int i;

    for (i = 0; i < size / sizeof (int64_t); i++)
        existing[i] = existing[i] + new[i];
}

static int
dt_aggregate_countcmp(int64_t *lhs, int64_t *rhs)
{
    int64_t lvar = *lhs;
    int64_t rvar = *rhs;

    if (lvar < rvar)
        return (DT_LESSTHAN);

    if (lvar > rvar)
        return (DT_GREATERTHAN);

    return (0);
}

/*ARGSUSED*/
static void
dt_aggregate_min(int64_t *existing, int64_t *new, size_t size)
{
    if (*new < *existing)
        *existing = *new;
}

/*ARGSUSED*/
static void
dt_aggregate_max(int64_t *existing, int64_t *new, size_t size)
{
    if (*new > *existing)
        *existing = *new;
}

static int
dt_aggregate_averagecmp(int64_t *lhs, int64_t *rhs)
{
    int64_t lavg = lhs[0] ? (lhs[1] / lhs[0]) : 0;
    int64_t ravg = rhs[0] ? (rhs[1] / rhs[0]) : 0;

    if (lavg < ravg)
        return (DT_LESSTHAN);

    if (lavg > ravg)
        return (DT_GREATERTHAN);

    return (0);
}

static int
dt_aggregate_stddevcmp(int64_t *lhs, int64_t *rhs)
{
    uint64_t lsd = dt_stddev((uint64_t *)lhs, 1);
    uint64_t rsd = dt_stddev((uint64_t *)rhs, 1);

    if (lsd < rsd)
        return (DT_LESSTHAN);

    if (lsd > rsd)
        return (DT_GREATERTHAN);

    return (0);
}

/*ARGSUSED*/
static void
dt_aggregate_lquantize(int64_t *existing, int64_t *new, size_t size)
{
    int64_t arg = *existing++;
    uint16_t levels = DTRACE_LQUANTIZE_LEVELS(arg);
    int i;

    for (i = 0; i <= levels + 1; i++)
        existing[i] = existing[i] + new[i + 1];
}

static long double
dt_aggregate_lquantizedsum(int64_t *lquanta)
{
    int64_t arg = *lquanta++;
    int32_t base = DTRACE_LQUANTIZE_BASE(arg);
    uint16_t step = DTRACE_LQUANTIZE_STEP(arg);
    uint16_t levels = DTRACE_LQUANTIZE_LEVELS(arg), i;
    long double total = (long double)lquanta[0] * (long double)(base - 1);

    for (i = 0; i < levels; base += step, i++)
        total += (long double)lquanta[i + 1] * (long double)base;

    return (total + (long double)lquanta[levels + 1] *
        (long double)(base + 1));
}

static int64_t
dt_aggregate_lquantizedzero(int64_t *lquanta)
{
    int64_t arg = *lquanta++;
    int32_t base = DTRACE_LQUANTIZE_BASE(arg);
    uint16_t step = DTRACE_LQUANTIZE_STEP(arg);
    uint16_t levels = DTRACE_LQUANTIZE_LEVELS(arg), i;

    if (base - 1 == 0)
        return (lquanta[0]);

    for (i = 0; i < levels; base += step, i++) {
        if (base != 0)
            continue;

        return (lquanta[i + 1]);
    }

    if (base + 1 == 0)
        return (lquanta[levels + 1]);

    return (0);
}

static int
dt_aggregate_lquantizedcmp(int64_t *lhs, int64_t *rhs)
{
    long double lsum = dt_aggregate_lquantizedsum(lhs);
    long double rsum = dt_aggregate_lquantizedsum(rhs);
    int64_t lzero, rzero;

    if (lsum < rsum)
        return (DT_LESSTHAN);

    if (lsum > rsum)
        return (DT_GREATERTHAN);

    /*
     * If they're both equal, then we will compare based on the weights at
     * zero.  If the weights at zero are equal (or if zero is not within
     * the range of the linear quantization), then this will be judged a
     * tie and will be resolved based on the key comparison.
     */
    lzero = dt_aggregate_lquantizedzero(lhs);
    rzero = dt_aggregate_lquantizedzero(rhs);

    if (lzero < rzero)
        return (DT_LESSTHAN);

    if (lzero > rzero)
        return (DT_GREATERTHAN);

    return (0);
}

static int
dt_aggregate_quantizedcmp(int64_t *lhs, int64_t *rhs)
{
    int nbuckets = DTRACE_QUANTIZE_NBUCKETS, i;
    long double ltotal = 0, rtotal = 0;
    int64_t lzero, rzero;

    for (i = 0; i < nbuckets; i++) {
        int64_t bucketval = DTRACE_QUANTIZE_BUCKETVAL(i);

        if (bucketval == 0) {
            lzero = lhs[i];
            rzero = rhs[i];
        }

        ltotal += (long double)bucketval * (long double)lhs[i];
        rtotal += (long double)bucketval * (long double)rhs[i];
    }

    if (ltotal < rtotal)
        return (DT_LESSTHAN);

    if (ltotal > rtotal)
        return (DT_GREATERTHAN);

    /*
     * If they're both equal, then we will compare based on the weights at
     * zero.  If the weights at zero are equal, then this will be judged a
     * tie and will be resolved based on the key comparison.
     */
    if (lzero < rzero)
        return (DT_LESSTHAN);

    if (lzero > rzero)
        return (DT_GREATERTHAN);

    return (0);
}

static void
dt_aggregate_usym(dtrace_hdl_t *dtp, uint64_t *data)
{
    uint64_t pid = data[0];
    uint64_t *pc = &data[1];
    struct ps_prochandle *P;
    GElf_Sym sym;

    if (dtp->dt_vector != NULL)
        return;

    if ((P = dt_proc_grab(dtp, pid, PGRAB_RDONLY | PGRAB_FORCE, 0)) == NULL)
        return;

    dt_proc_lock(dtp, P);

    if (Plookup_by_addr(P, *pc, NULL, 0, &sym) == 0)
        *pc = sym.st_value;

    dt_proc_unlock(dtp, P);
    dt_proc_release(dtp, P);
}

static void
dt_aggregate_umod(dtrace_hdl_t *dtp, uint64_t *data)
{
    uint64_t pid = data[0];
    uint64_t *pc = &data[1];
    struct ps_prochandle *P;
    const prmap_t *map;

    if (dtp->dt_vector != NULL)
        return;

    if ((P = dt_proc_grab(dtp, pid, PGRAB_RDONLY | PGRAB_FORCE, 0)) == NULL)
        return;

    dt_proc_lock(dtp, P);

    if ((map = Paddr_to_map(P, *pc)) != NULL)
        *pc = map->pr_vaddr;

    dt_proc_unlock(dtp, P);
    dt_proc_release(dtp, P);
}

static void
dt_aggregate_sym(dtrace_hdl_t *dtp, uint64_t *data)
{
    GElf_Sym sym;
    uint64_t *pc = data;

    if (dtrace_lookup_by_addr(dtp, *pc, &sym, NULL) == 0)
        *pc = sym.st_value;
}

static void
dt_aggregate_mod(dtrace_hdl_t *dtp, uint64_t *data)
{
    uint64_t *pc = data;
    dt_module_t *dmp;

    if (dtp->dt_vector != NULL) {
        /*
         * We don't have a way of just getting the module for a
         * vectored open, and it doesn't seem to be worth defining
         * one.  This means that use of mod() won't get true
         * aggregation in the postmortem case (some modules may
         * appear more than once in aggregation output).  It seems
         * unlikely that anyone will ever notice or care...
         */
        return;
    }

    for (dmp = dt_list_next(&dtp->dt_modlist); dmp != NULL;
        dmp = dt_list_next(dmp)) {
        if (*pc - dmp->dm_text_va < dmp->dm_text_size) {
            *pc = dmp->dm_text_va;
            return;
        }
    }
}

static dtrace_aggvarid_t
dt_aggregate_aggvarid(dt_ahashent_t *ent)
{
    dtrace_aggdesc_t *agg = ent->dtahe_data.dtada_desc;
    caddr_t data = ent->dtahe_data.dtada_data;
    dtrace_recdesc_t *rec = agg->dtagd_rec;

    /*
     * First, we'll check the variable ID in the aggdesc.  If it's valid,
     * we'll return it.  If not, we'll use the compiler-generated ID
     * present as the first record.
     */
    if (agg->dtagd_varid != DTRACE_AGGVARIDNONE)
        return (agg->dtagd_varid);

    agg->dtagd_varid = *((dtrace_aggvarid_t *)(uintptr_t)(data +
        rec->dtrd_offset));

    return (agg->dtagd_varid);
}


static void
dt_aggregate_expand_hash(dtrace_hdl_t *dtp, int *allocation_failed)

{
    int i;
    size_t size, old_size, new_size, ndx;
    dt_ahash_t new_hash;
    dt_ahashent_t *h, *moving;
    dt_aggregate_t *agp = &dtp->dt_aggregate;
    dt_ahash_t *hash = &agp->dtat_hash;

    /* Check to see if we're at the maximum size */
    if ((hash->dtah_sizendx + 1) >= DTRACE_NUM_AHASHSIZE) {
        *allocation_failed = 1;
        return;
    }

    /* First, allocate the new array; if we fail, we will not resize. */

    bzero(&new_hash, sizeof (dt_ahash_t));
    old_size = dtrace_ahashsize[hash->dtah_sizendx];
    hash->dtah_sizendx++;
    new_size = new_hash.dtah_size = dtrace_ahashsize[hash->dtah_sizendx];
    size = new_size * sizeof (dt_ahashent_t *);

    if ((new_hash.dtah_hash = malloc(size)) == NULL) {
        hash->dtah_sizendx--;
        *allocation_failed = 1;
        return;
    }

    bzero(new_hash.dtah_hash, size);
    for (i = 0; i < old_size; i++) {
        for (h = hash->dtah_hash[i]; h != NULL; ) {
            moving = h;
            h = h->dtahe_next;
            moving->dtahe_prev = NULL;
            ndx = moving->dtahe_hashval % new_size;
            if (new_hash.dtah_hash[ndx] != NULL)
                new_hash.dtah_hash[ndx]->dtahe_prev = moving;
            moving->dtahe_next = new_hash.dtah_hash[ndx];
            new_hash.dtah_hash[ndx] = moving;

            if (new_hash.dtah_all != NULL)
                new_hash.dtah_all->dtahe_prevall = moving;

            moving->dtahe_nextall = new_hash.dtah_all;
            new_hash.dtah_all = moving;
        }
    }

    /*
     * All moved, now update hash info.
     */
    hash->dtah_size = new_hash.dtah_size;
    free(hash->dtah_hash);
    hash->dtah_hash = new_hash.dtah_hash;
    hash->dtah_all = new_hash.dtah_all;
}

static int
dt_aggregate_snap_cpu(dtrace_hdl_t *dtp, processorid_t cpu)
{
    dtrace_epid_t id;
    uint64_t hashval;
    size_t offs, roffs, size, ndx;
    int i, j, rval;
    caddr_t addr, data;
    dtrace_recdesc_t *rec;
    dt_aggregate_t *agp = &dtp->dt_aggregate;
    dtrace_aggdesc_t *agg;
    dt_ahash_t *hash = &agp->dtat_hash;
    dtrace_bufdesc_t b = agp->dtat_buf, *buf = &b;
    dtrace_aggdata_t *aggdata;
    dt_ahashent_t *h;
    int flags = agp->dtat_flags;
    int allocation_failed = 0;

    buf->dtbd_cpu = cpu;

    if (dt_ioctl(dtp, DTRACEIOC_AGGSNAP, buf) == -1) {
        if (errno == ENOENT) {
            /*
             * If that failed with ENOENT, it may be because the
             * CPU was unconfigured.  This is okay; we'll just
             * do nothing but return success.
             */
            return (0);
        }

        return (dt_set_errno(dtp, errno));
    }

    if (buf->dtbd_drops != 0) {
        if (dt_handle_cpudrop(dtp, cpu,
            DTRACEDROP_AGGREGATION, buf->dtbd_drops) == -1)
            return (-1);
    }

    if (buf->dtbd_size == 0)
        return (0);

    if (hash->dtah_hash == NULL) {
        size_t size;

        hash->dtah_size = dtrace_ahashsize[hash->dtah_sizendx];
        size = hash->dtah_size * sizeof (dt_ahashent_t *);

        if ((hash->dtah_hash = malloc(size)) == NULL)
            return (dt_set_errno(dtp, EDT_NOMEM));
        bzero(hash->dtah_hash, size);
    }

    for (offs = 0; offs < buf->dtbd_size; ) {
        /*
         * We're guaranteed to have an ID.
         */
        id = *((dtrace_epid_t *)((uintptr_t)buf->dtbd_data +
            (uintptr_t)offs));

        if (id == DTRACE_AGGIDNONE) {
            /*
             * This is filler to assure proper alignment of the
             * next record; we simply ignore it.
             */
            offs += sizeof (id);
            continue;
        }

        if ((rval = dt_aggid_lookup(dtp, id, &agg)) != 0)
            return (rval);

        addr = buf->dtbd_data + offs;
        size = agg->dtagd_size;
        hashval = 0;

        for (j = 0; j < agg->dtagd_nrecs - 1; j++) {
            rec = &agg->dtagd_rec[j];
            roffs = rec->dtrd_offset;

            switch (rec->dtrd_action) {
            case DTRACEACT_USYM:
                dt_aggregate_usym(dtp,
                    /* LINTED - alignment */
                    (uint64_t *)&addr[roffs]);
                break;

            case DTRACEACT_UMOD:
                dt_aggregate_umod(dtp,
                    /* LINTED - alignment */
                    (uint64_t *)&addr[roffs]);
                break;

            case DTRACEACT_SYM:
                /* LINTED - alignment */
                dt_aggregate_sym(dtp, (uint64_t *)&addr[roffs]);
                break;

            case DTRACEACT_MOD:
                /* LINTED - alignment */
                dt_aggregate_mod(dtp, (uint64_t *)&addr[roffs]);
                break;

            default:
                break;
            }

            for (i = 0; i < rec->dtrd_size; i++) {
                DTRACE_AGG_HASH(hashval, addr, (roffs+i));
            }
        }

        /*
         * For locks (lockstat) things are int aligned, so we
         * are not using the entire hash.
         */

        ndx = hashval % dtrace_ahashsize[hash->dtah_sizendx];

        for (h = hash->dtah_hash[ndx]; h != NULL; h = h->dtahe_next) {
            if (h->dtahe_hashval != hashval)
                continue;

            if (h->dtahe_size != size)
                continue;

            aggdata = &h->dtahe_data;
            data = aggdata->dtada_data;

            for (j = 0; j < agg->dtagd_nrecs - 1; j++) {
                rec = &agg->dtagd_rec[j];
                roffs = rec->dtrd_offset;

                for (i = 0; i < rec->dtrd_size; i++) {
                    if (addr[roffs + i] != data[roffs + i])
                        goto hashnext;
                }
            }

            /*
             * We found it.  Now we need to apply the aggregating
             * action on the data here.
             */
            rec = &agg->dtagd_rec[agg->dtagd_nrecs - 1];
            roffs = rec->dtrd_offset;
            /* LINTED - alignment */
            h->dtahe_aggregate((int64_t *)&data[roffs],
                /* LINTED - alignment */
                (int64_t *)&addr[roffs], rec->dtrd_size);

            /*
             * If we're keeping per CPU data, apply the aggregating
             * action there as well.
             */
            if (aggdata->dtada_percpu != NULL) {
                data = aggdata->dtada_percpu[cpu];

                /* LINTED - alignment */
                h->dtahe_aggregate((int64_t *)data,
                    /* LINTED - alignment */
                    (int64_t *)&addr[roffs], rec->dtrd_size);
            }

            goto bufnext;
hashnext:
            continue;
        }

        /*
         * No entry for this record -- allocate a new one. Before doing
         * so, see if we should grow the hash.  (If it cannot be grown,
         * just add the entry to the existing hash.)
         */
        if ((hash->dtah_nent
            > (dtrace_ahashsize[hash->dtah_sizendx]*2)) &&
            !allocation_failed)
            dt_aggregate_expand_hash(dtp, &allocation_failed);

        if ((h = malloc(sizeof (dt_ahashent_t))) == NULL)
            return (dt_set_errno(dtp, EDT_NOMEM));
        bzero(h, sizeof (dt_ahashent_t));
        aggdata = &h->dtahe_data;

        if ((aggdata->dtada_data = malloc(size)) == NULL) {
            free(h);
            return (dt_set_errno(dtp, EDT_NOMEM));
        }

        bcopy(addr, aggdata->dtada_data, size);
        aggdata->dtada_size = size;
        aggdata->dtada_desc = agg;
        aggdata->dtada_handle = dtp;
        (void) dt_epid_lookup(dtp, agg->dtagd_epid,
            &aggdata->dtada_edesc, &aggdata->dtada_pdesc);
        aggdata->dtada_normal = 1;

        h->dtahe_hashval = hashval;
        h->dtahe_size = size;
        (void) dt_aggregate_aggvarid(h);

        rec = &agg->dtagd_rec[agg->dtagd_nrecs - 1];

        if (flags & DTRACE_A_PERCPU) {
            int max_cpus = agp->dtat_maxcpu;
            caddr_t *percpu = malloc(max_cpus * sizeof (caddr_t));

            if (percpu == NULL) {
                free(aggdata->dtada_data);
                free(h);
                return (dt_set_errno(dtp, EDT_NOMEM));
            }

            for (j = 0; j < max_cpus; j++) {
                percpu[j] = malloc(rec->dtrd_size);

                if (percpu[j] == NULL) {
                    while (--j >= 0)
                        free(percpu[j]);

                    free(aggdata->dtada_data);
                    free(h);
                    return (dt_set_errno(dtp, EDT_NOMEM));
                }

                if (j == cpu) {
                    bcopy(&addr[rec->dtrd_offset],
                        percpu[j], rec->dtrd_size);
                } else {
                    bzero(percpu[j], rec->dtrd_size);
                }
            }

            aggdata->dtada_percpu = percpu;
        }

        switch (rec->dtrd_action) {
        case DTRACEAGG_MIN:
            h->dtahe_aggregate = dt_aggregate_min;
            break;

        case DTRACEAGG_MAX:
            h->dtahe_aggregate = dt_aggregate_max;
            break;

        case DTRACEAGG_LQUANTIZE:
            h->dtahe_aggregate = dt_aggregate_lquantize;
            break;

        case DTRACEAGG_COUNT:
        case DTRACEAGG_SUM:
        case DTRACEAGG_AVG:
        case DTRACEAGG_STDDEV:
        case DTRACEAGG_QUANTIZE:
            h->dtahe_aggregate = dt_aggregate_count;
            break;

        default:
            return (dt_set_errno(dtp, EDT_BADAGG));
        }

        ndx = h->dtahe_hashval % hash->dtah_size;
        if (hash->dtah_hash[ndx] != NULL)
            hash->dtah_hash[ndx]->dtahe_prev = h;

        h->dtahe_next = hash->dtah_hash[ndx];
        hash->dtah_hash[ndx] = h;

        if (hash->dtah_all != NULL)
            hash->dtah_all->dtahe_prevall = h;

        h->dtahe_nextall = hash->dtah_all;
        hash->dtah_all = h;

        hash->dtah_nent++;
bufnext:
        offs += agg->dtagd_size;
    }
    return (0);
}

int
dtrace_aggregate_snap(dtrace_hdl_t *dtp)
{
    int i, rval;
    dt_aggregate_t *agp = &dtp->dt_aggregate;
    hrtime_t now = gethrtime();
    dtrace_optval_t interval = dtp->dt_options[DTRACEOPT_AGGRATE];

    if (dtp->dt_lastagg != 0) {
        if (now - dtp->dt_lastagg < interval)
            return (0);

        dtp->dt_lastagg += interval;
    } else {
        dtp->dt_lastagg = now;
    }

    if (!dtp->dt_active)
        return (dt_set_errno(dtp, EINVAL));

    if (agp->dtat_buf.dtbd_size == 0)
        return (0);

    for (i = 0; i < agp->dtat_ncpus; i++) {
        if (rval = dt_aggregate_snap_cpu(dtp, agp->dtat_cpus[i]))
            return (rval);
    }

    return (0);
}

static int
dt_aggregate_hashcmp(const void *lhs, const void *rhs)
{
    dt_ahashent_t *lh = *((dt_ahashent_t **)lhs);
    dt_ahashent_t *rh = *((dt_ahashent_t **)rhs);
    dtrace_aggdesc_t *lagg = lh->dtahe_data.dtada_desc;
    dtrace_aggdesc_t *ragg = rh->dtahe_data.dtada_desc;

    if (lagg->dtagd_nrecs < ragg->dtagd_nrecs)
        return (DT_LESSTHAN);

    if (lagg->dtagd_nrecs > ragg->dtagd_nrecs)
        return (DT_GREATERTHAN);

    return (0);
}

static int
dt_aggregate_varcmp(const void *lhs, const void *rhs)
{
    dt_ahashent_t *lh = *((dt_ahashent_t **)lhs);
    dt_ahashent_t *rh = *((dt_ahashent_t **)rhs);
    dtrace_aggvarid_t lid, rid;

    lid = dt_aggregate_aggvarid(lh);
    rid = dt_aggregate_aggvarid(rh);

    if (lid < rid)
        return (DT_LESSTHAN);

    if (lid > rid)
        return (DT_GREATERTHAN);

    return (0);
}

static int
dt_aggregate_keycmp(const void *lhs, const void *rhs)
{
    dt_ahashent_t *lh = *((dt_ahashent_t **)lhs);
    dt_ahashent_t *rh = *((dt_ahashent_t **)rhs);
    dtrace_aggdesc_t *lagg = lh->dtahe_data.dtada_desc;
    dtrace_aggdesc_t *ragg = rh->dtahe_data.dtada_desc;
    dtrace_recdesc_t *lrec, *rrec;
    char *ldata, *rdata;
    int rval, i, j, keypos, nrecs;

    if ((rval = dt_aggregate_hashcmp(lhs, rhs)) != 0)
        return (rval);

    nrecs = lagg->dtagd_nrecs - 1;
    assert(nrecs == ragg->dtagd_nrecs - 1);

    keypos = dt_keypos + 1 >= nrecs ? 0 : dt_keypos;

    for (i = 1; i < nrecs; i++) {
        uint64_t lval, rval;
        int ndx = i + keypos;

        if (ndx >= nrecs)
            ndx = ndx - nrecs + 1;

        lrec = &lagg->dtagd_rec[ndx];
        rrec = &ragg->dtagd_rec[ndx];

        ldata = lh->dtahe_data.dtada_data + lrec->dtrd_offset;
        rdata = rh->dtahe_data.dtada_data + rrec->dtrd_offset;

        if (lrec->dtrd_size < rrec->dtrd_size)
            return (DT_LESSTHAN);

        if (lrec->dtrd_size > rrec->dtrd_size)
            return (DT_GREATERTHAN);

        switch (lrec->dtrd_size) {
        case sizeof (uint64_t):
            /* LINTED - alignment */
            lval = *((uint64_t *)ldata);
            /* LINTED - alignment */
            rval = *((uint64_t *)rdata);
            break;

        case sizeof (uint32_t):
            /* LINTED - alignment */
            lval = *((uint32_t *)ldata);
            /* LINTED - alignment */
            rval = *((uint32_t *)rdata);
            break;

        case sizeof (uint16_t):
            /* LINTED - alignment */
            lval = *((uint16_t *)ldata);
            /* LINTED - alignment */
            rval = *((uint16_t *)rdata);
            break;

        case sizeof (uint8_t):
            lval = *((uint8_t *)ldata);
            rval = *((uint8_t *)rdata);
            break;

        default:
            switch (lrec->dtrd_action) {
            case DTRACEACT_UMOD:
            case DTRACEACT_UADDR:
            case DTRACEACT_USYM:
                for (j = 0; j < 2; j++) {
                    /* LINTED - alignment */
                    lval = ((uint64_t *)ldata)[j];
                    /* LINTED - alignment */
                    rval = ((uint64_t *)rdata)[j];

                    if (lval < rval)
                        return (DT_LESSTHAN);

                    if (lval > rval)
                        return (DT_GREATERTHAN);
                }

                break;

            default:
                for (j = 0; j < lrec->dtrd_size; j++) {
                    lval = ((uint8_t *)ldata)[j];
                    rval = ((uint8_t *)rdata)[j];

                    if (lval < rval)
                        return (DT_LESSTHAN);

                    if (lval > rval)
                        return (DT_GREATERTHAN);
                }
            }

            continue;
        }

        if (lval < rval)
            return (DT_LESSTHAN);

        if (lval > rval)
            return (DT_GREATERTHAN);
    }

    return (0);
}

static int
dt_aggregate_valcmp(const void *lhs, const void *rhs)
{
    dt_ahashent_t *lh = *((dt_ahashent_t **)lhs);
    dt_ahashent_t *rh = *((dt_ahashent_t **)rhs);
    dtrace_aggdesc_t *lagg = lh->dtahe_data.dtada_desc;
    dtrace_aggdesc_t *ragg = rh->dtahe_data.dtada_desc;
    caddr_t ldata = lh->dtahe_data.dtada_data;
    caddr_t rdata = rh->dtahe_data.dtada_data;
    dtrace_recdesc_t *lrec, *rrec;
    int64_t *laddr, *raddr;
    int rval, i;

    if ((rval = dt_aggregate_hashcmp(lhs, rhs)) != 0)
        return (rval);

    if (lagg->dtagd_nrecs > ragg->dtagd_nrecs)
        return (DT_GREATERTHAN);

    if (lagg->dtagd_nrecs < ragg->dtagd_nrecs)
        return (DT_LESSTHAN);

    for (i = 0; i < lagg->dtagd_nrecs; i++) {
        lrec = &lagg->dtagd_rec[i];
        rrec = &ragg->dtagd_rec[i];

        if (lrec->dtrd_offset < rrec->dtrd_offset)
            return (DT_LESSTHAN);

        if (lrec->dtrd_offset > rrec->dtrd_offset)
            return (DT_GREATERTHAN);

        if (lrec->dtrd_action < rrec->dtrd_action)
            return (DT_LESSTHAN);

        if (lrec->dtrd_action > rrec->dtrd_action)
            return (DT_GREATERTHAN);
    }

    laddr = (int64_t *)(uintptr_t)(ldata + lrec->dtrd_offset);
    raddr = (int64_t *)(uintptr_t)(rdata + rrec->dtrd_offset);

    switch (lrec->dtrd_action) {
    case DTRACEAGG_AVG:
        rval = dt_aggregate_averagecmp(laddr, raddr);
        break;

    case DTRACEAGG_STDDEV:
        rval = dt_aggregate_stddevcmp(laddr, raddr);
        break;

    case DTRACEAGG_QUANTIZE:
        rval = dt_aggregate_quantizedcmp(laddr, raddr);
        break;

    case DTRACEAGG_LQUANTIZE:
        rval = dt_aggregate_lquantizedcmp(laddr, raddr);
        break;

    case DTRACEAGG_COUNT:
    case DTRACEAGG_SUM:
    case DTRACEAGG_MIN:
    case DTRACEAGG_MAX:
        rval = dt_aggregate_countcmp(laddr, raddr);
        break;

    default:
        assert(0);
    }

    return (rval);
}

static int
dt_aggregate_valkeycmp(const void *lhs, const void *rhs)
{
    int rval;

    if ((rval = dt_aggregate_valcmp(lhs, rhs)) != 0)
        return (rval);

    /*
     * If we're here, the values for the two aggregation elements are
     * equal.  We already know that the key layout is the same for the two
     * elements; we must now compare the keys themselves as a tie-breaker.
     */
    return (dt_aggregate_keycmp(lhs, rhs));
}

static int
dt_aggregate_keyvarcmp(const void *lhs, const void *rhs)
{
    int rval;

    if ((rval = dt_aggregate_keycmp(lhs, rhs)) != 0)
        return (rval);

    return (dt_aggregate_varcmp(lhs, rhs));
}

static int
dt_aggregate_varkeycmp(const void *lhs, const void *rhs)
{
    int rval;

    if ((rval = dt_aggregate_varcmp(lhs, rhs)) != 0)
        return (rval);

    return (dt_aggregate_keycmp(lhs, rhs));
}

static int
dt_aggregate_valvarcmp(const void *lhs, const void *rhs)
{
    int rval;

    if ((rval = dt_aggregate_valkeycmp(lhs, rhs)) != 0)
        return (rval);

    return (dt_aggregate_varcmp(lhs, rhs));
}

static int
dt_aggregate_varvalcmp(const void *lhs, const void *rhs)
{
    int rval;

    if ((rval = dt_aggregate_varcmp(lhs, rhs)) != 0)
        return (rval);

    return (dt_aggregate_valkeycmp(lhs, rhs));
}

static int
dt_aggregate_keyvarrevcmp(const void *lhs, const void *rhs)
{
    return (dt_aggregate_keyvarcmp(rhs, lhs));
}

static int
dt_aggregate_varkeyrevcmp(const void *lhs, const void *rhs)
{
    return (dt_aggregate_varkeycmp(rhs, lhs));
}

static int
dt_aggregate_valvarrevcmp(const void *lhs, const void *rhs)
{
    return (dt_aggregate_valvarcmp(rhs, lhs));
}

static int
dt_aggregate_varvalrevcmp(const void *lhs, const void *rhs)
{
    return (dt_aggregate_varvalcmp(rhs, lhs));
}

static int
dt_aggregate_bundlecmp(const void *lhs, const void *rhs)
{
    dt_ahashent_t **lh = *((dt_ahashent_t ***)lhs);
    dt_ahashent_t **rh = *((dt_ahashent_t ***)rhs);
    int i, rval;

    if (dt_keysort) {
        /*
         * If we're sorting on keys, we need to scan until we find the
         * last entry -- that's the representative key.  (The order of
         * the bundle is values followed by key to accommodate the
         * default behavior of sorting by value.)  If the keys are
         * equal, we'll fall into the value comparison loop, below.
         */
        for (i = 0; lh[i + 1] != NULL; i++)
            continue;

        assert(i != 0);
        assert(rh[i + 1] == NULL);

        if ((rval = dt_aggregate_keycmp(&lh[i], &rh[i])) != 0)
            return (rval);
    }

    for (i = 0; ; i++) {
        if (lh[i + 1] == NULL) {
            /*
             * All of the values are equal; if we're sorting on
             * keys, then we're only here because the keys were
             * found to be equal and these records are therefore
             * equal.  If we're not sorting on keys, we'll use the
             * key comparison from the representative key as the
             * tie-breaker.
             */
            if (dt_keysort)
                return (0);

            assert(i != 0);
            assert(rh[i + 1] == NULL);
            return (dt_aggregate_keycmp(&lh[i], &rh[i]));
        } else {
            if ((rval = dt_aggregate_valcmp(&lh[i], &rh[i])) != 0)
                return (rval);
        }
    }
}

int
dt_aggregate_go(dtrace_hdl_t *dtp)
{
    dt_aggregate_t *agp = &dtp->dt_aggregate;
    dtrace_optval_t size, cpu;
    dtrace_bufdesc_t *buf = &agp->dtat_buf;
    int rval, i;

    assert(agp->dtat_maxcpu == 0);
    assert(agp->dtat_ncpu == 0);
    assert(agp->dtat_cpus == NULL);

    agp->dtat_maxcpu = dt_sysconf(dtp, _SC_CPUID_MAX) + 1;
    agp->dtat_ncpu = dt_sysconf(dtp, _SC_NPROCESSORS_MAX);
    agp->dtat_cpus = malloc(agp->dtat_ncpu * sizeof (processorid_t));

    if (agp->dtat_cpus == NULL)
        return (dt_set_errno(dtp, EDT_NOMEM));

    /*
     * Use the aggregation buffer size as reloaded from the kernel.
     */
    size = dtp->dt_options[DTRACEOPT_AGGSIZE];

    rval = dtrace_getopt(dtp, "aggsize", &size);
    assert(rval == 0);

    if (size == 0 || size == DTRACEOPT_UNSET)
        return (0);

    buf = &agp->dtat_buf;
    buf->dtbd_size = size;

    if ((buf->dtbd_data = malloc(buf->dtbd_size)) == NULL)
        return (dt_set_errno(dtp, EDT_NOMEM));

    /*
     * Now query for the CPUs enabled.
     */
    rval = dtrace_getopt(dtp, "cpu", &cpu);
    assert(rval == 0 && cpu != DTRACEOPT_UNSET);

    if (cpu != DTRACE_CPUALL) {
        assert(cpu < agp->dtat_ncpu);
        agp->dtat_cpus[agp->dtat_ncpus++] = (processorid_t)cpu;

        return (0);
    }

    agp->dtat_ncpus = 0;
    for (i = 0; i < agp->dtat_maxcpu; i++) {
        if (dt_status(dtp, i) == -1)
            continue;

        agp->dtat_cpus[agp->dtat_ncpus++] = i;
    }

    return (0);
}

static int
dt_aggwalk_rval(dtrace_hdl_t *dtp, dt_ahashent_t *h, int rval)
{
    dt_aggregate_t *agp = &dtp->dt_aggregate;
    dtrace_aggdata_t *data;
    dtrace_aggdesc_t *aggdesc;
    dtrace_recdesc_t *rec;
    int i;

    switch (rval) {
    case DTRACE_AGGWALK_NEXT:
        break;

    case DTRACE_AGGWALK_CLEAR: {
        uint32_t size, offs = 0;

        aggdesc = h->dtahe_data.dtada_desc;
        rec = &aggdesc->dtagd_rec[aggdesc->dtagd_nrecs - 1];
        size = rec->dtrd_size;
        data = &h->dtahe_data;

        if (rec->dtrd_action == DTRACEAGG_LQUANTIZE) {
            offs = sizeof (uint64_t);
            size -= sizeof (uint64_t);
        }

        bzero(&data->dtada_data[rec->dtrd_offset] + offs, size);

        if (data->dtada_percpu == NULL)
            break;

        for (i = 0; i < dtp->dt_aggregate.dtat_maxcpu; i++)
            bzero(data->dtada_percpu[i] + offs, size);
        break;
    }

    case DTRACE_AGGWALK_ERROR:
        /*
         * We assume that errno is already set in this case.
         */
        return (dt_set_errno(dtp, errno));

    case DTRACE_AGGWALK_ABORT:
        return (dt_set_errno(dtp, EDT_DIRABORT));

    case DTRACE_AGGWALK_DENORMALIZE:
        h->dtahe_data.dtada_normal = 1;
        return (0);

    case DTRACE_AGGWALK_NORMALIZE:
        if (h->dtahe_data.dtada_normal == 0) {
            h->dtahe_data.dtada_normal = 1;
            return (dt_set_errno(dtp, EDT_BADRVAL));
        }

        return (0);

    case DTRACE_AGGWALK_REMOVE: {
        dtrace_aggdata_t *aggdata = &h->dtahe_data;
        int i, max_cpus = agp->dtat_maxcpu;

        /*
         * First, remove this hash entry from its hash chain.
         */
        if (h->dtahe_prev != NULL) {
            h->dtahe_prev->dtahe_next = h->dtahe_next;
        } else {
            dt_ahash_t *hash = &agp->dtat_hash;
            size_t ndx = h->dtahe_hashval % hash->dtah_size;

            assert(hash->dtah_hash[ndx] == h);
            hash->dtah_hash[ndx] = h->dtahe_next;
        }

        if (h->dtahe_next != NULL)
            h->dtahe_next->dtahe_prev = h->dtahe_prev;

        /*
         * Now remove it from the list of all hash entries.
         */
        if (h->dtahe_prevall != NULL) {
            h->dtahe_prevall->dtahe_nextall = h->dtahe_nextall;
        } else {
            dt_ahash_t *hash = &agp->dtat_hash;

            assert(hash->dtah_all == h);
            hash->dtah_all = h->dtahe_nextall;
        }

        if (h->dtahe_nextall != NULL)
            h->dtahe_nextall->dtahe_prevall = h->dtahe_prevall;

        (agp->dtat_hash).dtah_nent--;

        /*
         * We're unlinked.  We can safely destroy the data.
         */
        if (aggdata->dtada_percpu != NULL) {
            for (i = 0; i < max_cpus; i++)
                free(aggdata->dtada_percpu[i]);
            free(aggdata->dtada_percpu);
        }

        free(aggdata->dtada_data);
        free(h);

        return (0);
    }

    default:
        return (dt_set_errno(dtp, EDT_BADRVAL));
    }

    return (0);
}

void
dt_aggregate_qsort(dtrace_hdl_t *dtp, void *base, size_t nel, size_t width,
    int (*compar)(const void *, const void *))
{
    int rev = dt_revsort, key = dt_keysort, keypos = dt_keypos;
    dtrace_optval_t keyposopt = dtp->dt_options[DTRACEOPT_AGGSORTKEYPOS];

    dt_revsort = (dtp->dt_options[DTRACEOPT_AGGSORTREV] != DTRACEOPT_UNSET);
    dt_keysort = (dtp->dt_options[DTRACEOPT_AGGSORTKEY] != DTRACEOPT_UNSET);

    if (keyposopt != DTRACEOPT_UNSET && keyposopt <= INT_MAX) {
        dt_keypos = (int)keyposopt;
    } else {
        dt_keypos = 0;
    }

    if (compar == NULL) {
        if (!dt_keysort) {
            compar = dt_aggregate_varvalcmp;
        } else {
            compar = dt_aggregate_varkeycmp;
        }
    }

    qsort(base, nel, width, compar);

    dt_revsort = rev;
    dt_keysort = key;
    dt_keypos = keypos;
}

int
dtrace_aggregate_walk(dtrace_hdl_t *dtp, dtrace_aggregate_f *func, void *arg)
{
    dt_ahashent_t *h, *next;
    dt_ahash_t *hash = &dtp->dt_aggregate.dtat_hash;

    for (h = hash->dtah_all; h != NULL; h = next) {
        /*
         * dt_aggwalk_rval() can potentially remove the current hash
         * entry; we need to load the next hash entry before calling
         * into it.
         */
        next = h->dtahe_nextall;

        if (dt_aggwalk_rval(dtp, h, func(&h->dtahe_data, arg)) == -1)
            return (-1);
    }

    return (0);
}

static int
dt_aggregate_walk_sorted(dtrace_hdl_t *dtp,
    dtrace_aggregate_f *func, void *arg,
    int (*sfunc)(const void *, const void *))
{
    dt_aggregate_t *agp = &dtp->dt_aggregate;
    dt_ahashent_t *h, **sorted;
    dt_ahash_t *hash = &agp->dtat_hash;
    size_t i, nentries = 0;

    for (h = hash->dtah_all; h != NULL; h = h->dtahe_nextall)
        nentries++;

    sorted = dt_alloc(dtp, nentries * sizeof (dt_ahashent_t *));

    if (sorted == NULL)
        return (-1);

    for (h = hash->dtah_all, i = 0; h != NULL; h = h->dtahe_nextall)
        sorted[i++] = h;

    (void) pthread_mutex_lock(&dt_qsort_lock);

    if (sfunc == NULL) {
        dt_aggregate_qsort(dtp, sorted, nentries,
            sizeof (dt_ahashent_t *), NULL);
    } else {
        /*
         * If we've been explicitly passed a sorting function,
         * we'll use that -- ignoring the values of the "aggsortrev",
         * "aggsortkey" and "aggsortkeypos" options.
         */
        qsort(sorted, nentries, sizeof (dt_ahashent_t *), sfunc);
    }

    (void) pthread_mutex_unlock(&dt_qsort_lock);

    for (i = 0; i < nentries; i++) {
        h = sorted[i];

        if (dt_aggwalk_rval(dtp, h, func(&h->dtahe_data, arg)) == -1) {
            dt_free(dtp, sorted);
            return (-1);
        }
    }

    dt_free(dtp, sorted);
    return (0);
}

int
dtrace_aggregate_walk_sorted(dtrace_hdl_t *dtp,
    dtrace_aggregate_f *func, void *arg)
{
    return (dt_aggregate_walk_sorted(dtp, func, arg, NULL));
}

int
dtrace_aggregate_walk_keysorted(dtrace_hdl_t *dtp,
    dtrace_aggregate_f *func, void *arg)
{
    return (dt_aggregate_walk_sorted(dtp, func,
        arg, dt_aggregate_varkeycmp));
}

int
dtrace_aggregate_walk_valsorted(dtrace_hdl_t *dtp,
    dtrace_aggregate_f *func, void *arg)
{
    return (dt_aggregate_walk_sorted(dtp, func,
        arg, dt_aggregate_varvalcmp));
}

int
dtrace_aggregate_walk_keyvarsorted(dtrace_hdl_t *dtp,
    dtrace_aggregate_f *func, void *arg)
{
    return (dt_aggregate_walk_sorted(dtp, func,
        arg, dt_aggregate_keyvarcmp));
}

int
dtrace_aggregate_walk_valvarsorted(dtrace_hdl_t *dtp,
    dtrace_aggregate_f *func, void *arg)
{
    return (dt_aggregate_walk_sorted(dtp, func,
        arg, dt_aggregate_valvarcmp));
}

int
dtrace_aggregate_walk_keyrevsorted(dtrace_hdl_t *dtp,
    dtrace_aggregate_f *func, void *arg)
{
    return (dt_aggregate_walk_sorted(dtp, func,
        arg, dt_aggregate_varkeyrevcmp));
}

int
dtrace_aggregate_walk_valrevsorted(dtrace_hdl_t *dtp,
    dtrace_aggregate_f *func, void *arg)
{
    return (dt_aggregate_walk_sorted(dtp, func,
        arg, dt_aggregate_varvalrevcmp));
}

int
dtrace_aggregate_walk_keyvarrevsorted(dtrace_hdl_t *dtp,
    dtrace_aggregate_f *func, void *arg)
{
    return (dt_aggregate_walk_sorted(dtp, func,
        arg, dt_aggregate_keyvarrevcmp));
}

int
dtrace_aggregate_walk_valvarrevsorted(dtrace_hdl_t *dtp,
    dtrace_aggregate_f *func, void *arg)
{
    return (dt_aggregate_walk_sorted(dtp, func,
        arg, dt_aggregate_valvarrevcmp));
}

int
dtrace_aggregate_walk_joined(dtrace_hdl_t *dtp, dtrace_aggvarid_t *aggvars,
    int naggvars, dtrace_aggregate_walk_joined_f *func, void *arg)
{
    dt_aggregate_t *agp = &dtp->dt_aggregate;
    dt_ahashent_t *h, **sorted = NULL, ***bundle, **nbundle;
    const dtrace_aggdata_t **data;
    dt_ahashent_t *zaggdata = NULL;
    dt_ahash_t *hash = &agp->dtat_hash;
    size_t nentries = 0, nbundles = 0, start, zsize = 0, bundlesize;
    dtrace_aggvarid_t max = 0, aggvar;
    int rval = -1, *map, *remap = NULL;
    int i, j;
    dtrace_optval_t sortpos = dtp->dt_options[DTRACEOPT_AGGSORTPOS];

    /*
     * If the sorting position is greater than the number of aggregation
     * variable IDs, we silently set it to 0.
     */
    if (sortpos == DTRACEOPT_UNSET || sortpos >= naggvars)
        sortpos = 0;

    /*
     * First we need to translate the specified aggregation variable IDs
     * into a linear map that will allow us to translate an aggregation
     * variable ID into its position in the specified aggvars.
     */
    for (i = 0; i < naggvars; i++) {
        if (aggvars[i] == DTRACE_AGGVARIDNONE || aggvars[i] < 0)
            return (dt_set_errno(dtp, EDT_BADAGGVAR));

        if (aggvars[i] > max)
            max = aggvars[i];
    }

    if ((map = dt_zalloc(dtp, (max + 1) * sizeof (int))) == NULL)
        return (-1);

    zaggdata = dt_zalloc(dtp, naggvars * sizeof (dt_ahashent_t));

    if (zaggdata == NULL)
        goto out;

    for (i = 0; i < naggvars; i++) {
        int ndx = i + sortpos;

        if (ndx >= naggvars)
            ndx -= naggvars;

        aggvar = aggvars[ndx];
        assert(aggvar <= max);

        if (map[aggvar]) {
            /*
             * We have an aggregation variable that is present
             * more than once in the array of aggregation
             * variables.  While it's unclear why one might want
             * to do this, it's legal.  To support this construct,
             * we will allocate a remap that will indicate the
             * position from which this aggregation variable
             * should be pulled.  (That is, where the remap will
             * map from one position to another.)
             */
            if (remap == NULL) {
                remap = dt_zalloc(dtp, naggvars * sizeof (int));

                if (remap == NULL)
                    goto out;
            }

            /*
             * Given that the variable is already present, assert
             * that following through the mapping and adjusting
             * for the sort position yields the same aggregation
             * variable ID.
             */
            assert(aggvars[(map[aggvar] - 1 + sortpos) %
                naggvars] == aggvars[ndx]);

            remap[i] = map[aggvar];
            continue;
        }

        map[aggvar] = i + 1;
    }

    /*
     * We need to take two passes over the data to size our allocation, so
     * we'll use the first pass to also fill in the zero-filled data to be
     * used to properly format a zero-valued aggregation.
     */
    for (h = hash->dtah_all; h != NULL; h = h->dtahe_nextall) {
        dtrace_aggvarid_t id;
        int ndx;

        if ((id = dt_aggregate_aggvarid(h)) > max || !(ndx = map[id]))
            continue;

        if (zaggdata[ndx - 1].dtahe_size == 0) {
            zaggdata[ndx - 1].dtahe_size = h->dtahe_size;
            zaggdata[ndx - 1].dtahe_data = h->dtahe_data;
        }

        nentries++;
    }

    if (nentries == 0) {
        /*
         * We couldn't find any entries; there is nothing else to do.
         */
        rval = 0;
        goto out;
    }

    /*
     * Before we sort the data, we're going to look for any holes in our
     * zero-filled data.  This will occur if an aggregation variable that
     * we are being asked to print has not yet been assigned the result of
     * any aggregating action for _any_ tuple.  The issue becomes that we
     * would like a zero value to be printed for all columns for this
     * aggregation, but without any record description, we don't know the
     * aggregating action that corresponds to the aggregation variable.  To
     * try to find a match, we're simply going to lookup aggregation IDs
     * (which are guaranteed to be contiguous and to start from 1), looking
     * for the specified aggregation variable ID.  If we find a match,
     * we'll use that.  If we iterate over all aggregation IDs and don't
     * find a match, then we must be an anonymous enabling.  (Anonymous
     * enablings can't currently derive either aggregation variable IDs or
     * aggregation variable names given only an aggregation ID.)  In this
     * obscure case (anonymous enabling, multiple aggregation printa() with
     * some aggregations not represented for any tuple), our defined
     * behavior is that the zero will be printed in the format of the first
     * aggregation variable that contains any non-zero value.
     */
    for (i = 0; i < naggvars; i++) {
        if (zaggdata[i].dtahe_size == 0) {
            dtrace_aggvarid_t aggvar;

            aggvar = aggvars[(i - sortpos + naggvars) % naggvars];
            assert(zaggdata[i].dtahe_data.dtada_data == NULL);

            for (j = DTRACE_AGGIDNONE + 1; ; j++) {
                dtrace_aggdesc_t *agg;
                dtrace_aggdata_t *aggdata;

                if (dt_aggid_lookup(dtp, j, &agg) != 0)
                    break;

                if (agg->dtagd_varid != aggvar)
                    continue;

                /*
                 * We have our description -- now we need to
                 * cons up the zaggdata entry for it.
                 */
                aggdata = &zaggdata[i].dtahe_data;
                aggdata->dtada_size = agg->dtagd_size;
                aggdata->dtada_desc = agg;
                aggdata->dtada_handle = dtp;
                (void) dt_epid_lookup(dtp, agg->dtagd_epid,
                    &aggdata->dtada_edesc,
                    &aggdata->dtada_pdesc);
                aggdata->dtada_normal = 1;
                zaggdata[i].dtahe_hashval = 0;
                zaggdata[i].dtahe_size = agg->dtagd_size;
                break;
            }

            if (zaggdata[i].dtahe_size == 0) {
                caddr_t data;

                /*
                 * We couldn't find this aggregation, meaning
                 * that we have never seen it before for any
                 * tuple _and_ this is an anonymous enabling.
                 * That is, we're in the obscure case outlined
                 * above.  In this case, our defined behavior
                 * is to format the data in the format of the
                 * first non-zero aggregation -- of which, of
                 * course, we know there to be at least one
                 * (or nentries would have been zero).
                 */
                for (j = 0; j < naggvars; j++) {
                    if (zaggdata[j].dtahe_size != 0)
                        break;
                }

                assert(j < naggvars);
                zaggdata[i] = zaggdata[j];

                data = zaggdata[i].dtahe_data.dtada_data;
                assert(data != NULL);
            }
        }
    }

    /*
     * Now we need to allocate our zero-filled data for use for
     * aggregations that don't have a value corresponding to a given key.
     */
    for (i = 0; i < naggvars; i++) {
        dtrace_aggdata_t *aggdata = &zaggdata[i].dtahe_data;
        dtrace_aggdesc_t *aggdesc = aggdata->dtada_desc;
        dtrace_recdesc_t *rec;
        uint64_t larg;
        caddr_t zdata;

        zsize = zaggdata[i].dtahe_size;
        assert(zsize != 0);

        if ((zdata = dt_zalloc(dtp, zsize)) == NULL) {
            /*
             * If we failed to allocated some zero-filled data, we
             * need to zero out the remaining dtada_data pointers
             * to prevent the wrong data from being freed below.
             */
            for (j = i; j < naggvars; j++)
                zaggdata[j].dtahe_data.dtada_data = NULL;
            goto out;
        }

        aggvar = aggvars[(i - sortpos + naggvars) % naggvars];

        /*
         * First, the easy bit.  To maintain compatibility with
         * consumers that pull the compiler-generated ID out of the
         * data, we put that ID at the top of the zero-filled data.
         */
        rec = &aggdesc->dtagd_rec[0];
        /* LINTED - alignment */
        *((dtrace_aggvarid_t *)(zdata + rec->dtrd_offset)) = aggvar;

        rec = &aggdesc->dtagd_rec[aggdesc->dtagd_nrecs - 1];

        /*
         * Now for the more complicated part.  If (and only if) this
         * is an lquantize() aggregating action, zero-filled data is
         * not equivalent to an empty record:  we must also get the
         * parameters for the lquantize().
         */
        if (rec->dtrd_action == DTRACEAGG_LQUANTIZE) {
            if (aggdata->dtada_data != NULL) {
                /*
                 * The easier case here is if we actually have
                 * some prototype data -- in which case we
                 * manually dig it out of the aggregation
                 * record.
                 */
                /* LINTED - alignment */
                larg = *((uint64_t *)(aggdata->dtada_data +
                    rec->dtrd_offset));
            } else {
                /*
                 * We don't have any prototype data.  As a
                 * result, we know that we _do_ have the
                 * compiler-generated information.  (If this
                 * were an anonymous enabling, all of our
                 * zero-filled data would have prototype data
                 * -- either directly or indirectly.) So as
                 * gross as it is, we'll grovel around in the
                 * compiler-generated information to find the
                 * lquantize() parameters.
                 */
                dtrace_stmtdesc_t *sdp;
                dt_ident_t *aid;
                dt_idsig_t *isp;

                sdp = (dtrace_stmtdesc_t *)(uintptr_t)
                    aggdesc->dtagd_rec[0].dtrd_uarg;
                aid = sdp->dtsd_aggdata;
                isp = (dt_idsig_t *)aid->di_data;
                assert(isp->dis_auxinfo != 0);
                larg = isp->dis_auxinfo;
            }

            /* LINTED - alignment */
            *((uint64_t *)(zdata + rec->dtrd_offset)) = larg;
        }

        aggdata->dtada_data = zdata;
    }

    /*
     * Now that we've dealt with setting up our zero-filled data, we can
     * allocate our sorted array, and take another pass over the data to
     * fill it.
     */
    sorted = dt_alloc(dtp, nentries * sizeof (dt_ahashent_t *));

    if (sorted == NULL)
        goto out;

    for (h = hash->dtah_all, i = 0; h != NULL; h = h->dtahe_nextall) {
        dtrace_aggvarid_t id;

        if ((id = dt_aggregate_aggvarid(h)) > max || !map[id])
            continue;

        sorted[i++] = h;
    }

    assert(i == nentries);

    /*
     * We've loaded our array; now we need to sort by value to allow us
     * to create bundles of like value.  We're going to acquire the
     * dt_qsort_lock here, and hold it across all of our subsequent
     * comparison and sorting.
     */
    (void) pthread_mutex_lock(&dt_qsort_lock);

    qsort(sorted, nentries, sizeof (dt_ahashent_t *),
        dt_aggregate_keyvarcmp);

    /*
     * Now we need to go through and create bundles.  Because the number
     * of bundles is bounded by the size of the sorted array, we're going
     * to reuse the underlying storage.  And note that "bundle" is an
     * array of pointers to arrays of pointers to dt_ahashent_t -- making
     * its type (regrettably) "dt_ahashent_t ***".  (Regrettable because
     * '*' -- like '_' and 'X' -- should never appear in triplicate in
     * an ideal world.)
     */
    bundle = (dt_ahashent_t ***)sorted;

    for (i = 1, start = 0; i <= nentries; i++) {
        if (i < nentries &&
            dt_aggregate_keycmp(&sorted[i], &sorted[i - 1]) == 0)
            continue;

        /*
         * We have a bundle boundary.  Everything from start to
         * (i - 1) belongs in one bundle.
         */
        assert(i - start <= naggvars);
        bundlesize = (naggvars + 2) * sizeof (dt_ahashent_t *);

        if ((nbundle = dt_zalloc(dtp, bundlesize)) == NULL) {
            (void) pthread_mutex_unlock(&dt_qsort_lock);
            goto out;
        }

        for (j = start; j < i; j++) {
            dtrace_aggvarid_t id = dt_aggregate_aggvarid(sorted[j]);

            assert(id <= max);
            assert(map[id] != 0);
            assert(map[id] - 1 < naggvars);
            assert(nbundle[map[id] - 1] == NULL);
            nbundle[map[id] - 1] = sorted[j];

            if (nbundle[naggvars] == NULL)
                nbundle[naggvars] = sorted[j];
        }

        for (j = 0; j < naggvars; j++) {
            if (nbundle[j] != NULL)
                continue;

            /*
             * Before we assume that this aggregation variable
             * isn't present (and fall back to using the
             * zero-filled data allocated earlier), check the
             * remap.  If we have a remapping, we'll drop it in
             * here.  Note that we might be remapping an
             * aggregation variable that isn't present for this
             * key; in this case, the aggregation data that we
             * copy will point to the zeroed data.
             */
            if (remap != NULL && remap[j]) {
                assert(remap[j] - 1 < j);
                assert(nbundle[remap[j] - 1] != NULL);
                nbundle[j] = nbundle[remap[j] - 1];
            } else {
                nbundle[j] = &zaggdata[j];
            }
        }

        bundle[nbundles++] = nbundle;
        start = i;
    }

    /*
     * Now we need to re-sort based on the first value.
     */
    dt_aggregate_qsort(dtp, bundle, nbundles, sizeof (dt_ahashent_t **),
        dt_aggregate_bundlecmp);

    (void) pthread_mutex_unlock(&dt_qsort_lock);

    /*
     * We're done!  Now we just need to go back over the sorted bundles,
     * calling the function.
     */
    data = alloca((naggvars + 1) * sizeof (dtrace_aggdata_t *));

    for (i = 0; i < nbundles; i++) {
        for (j = 0; j < naggvars; j++)
            data[j + 1] = NULL;

        for (j = 0; j < naggvars; j++) {
            int ndx = j - sortpos;

            if (ndx < 0)
                ndx += naggvars;

            assert(bundle[i][ndx] != NULL);
            data[j + 1] = &bundle[i][ndx]->dtahe_data;
        }

        for (j = 0; j < naggvars; j++)
            assert(data[j + 1] != NULL);

        /*
         * The representative key is the last element in the bundle.
         * Assert that we have one, and then set it to be the first
         * element of data.
         */
        assert(bundle[i][j] != NULL);
        data[0] = &bundle[i][j]->dtahe_data;

        if ((rval = func(data, naggvars + 1, arg)) == -1)
            goto out;
    }

    rval = 0;
out:
    for (i = 0; i < nbundles; i++)
        dt_free(dtp, bundle[i]);

    if (zaggdata != NULL) {
        for (i = 0; i < naggvars; i++)
            dt_free(dtp, zaggdata[i].dtahe_data.dtada_data);
    }

    dt_free(dtp, zaggdata);
    dt_free(dtp, sorted);
    dt_free(dtp, remap);
    dt_free(dtp, map);

    return (rval);
}

int
dtrace_aggregate_print(dtrace_hdl_t *dtp, FILE *fp,
    dtrace_aggregate_walk_f *func)
{
    dt_print_aggdata_t pd;

    pd.dtpa_dtp = dtp;
    pd.dtpa_fp = fp;
    pd.dtpa_allunprint = 1;

    if (func == NULL)
        func = dtrace_aggregate_walk_sorted;

    if ((*func)(dtp, dt_print_agg, &pd) == -1)
        return (dt_set_errno(dtp, dtp->dt_errno));

    return (0);
}

void
dtrace_aggregate_clear(dtrace_hdl_t *dtp)
{
    dt_aggregate_t *agp = &dtp->dt_aggregate;
    dt_ahash_t *hash = &agp->dtat_hash;
    dt_ahashent_t *h;
    dtrace_aggdata_t *data;
    dtrace_aggdesc_t *aggdesc;
    dtrace_recdesc_t *rec;
    int i, max_cpus = agp->dtat_maxcpu;

    for (h = hash->dtah_all; h != NULL; h = h->dtahe_nextall) {
        aggdesc = h->dtahe_data.dtada_desc;
        rec = &aggdesc->dtagd_rec[aggdesc->dtagd_nrecs - 1];
        data = &h->dtahe_data;

        bzero(&data->dtada_data[rec->dtrd_offset], rec->dtrd_size);

        if (data->dtada_percpu == NULL)
            continue;

        for (i = 0; i < max_cpus; i++)
            bzero(data->dtada_percpu[i], rec->dtrd_size);
    }
}

void
dt_aggregate_destroy(dtrace_hdl_t *dtp)
{
    dt_aggregate_t *agp = &dtp->dt_aggregate;
    dt_ahash_t *hash = &agp->dtat_hash;
    dt_ahashent_t *h, *next;
    dtrace_aggdata_t *aggdata;
    int i, max_cpus = agp->dtat_maxcpu;

    if (hash->dtah_hash == NULL) {
        assert(hash->dtah_all == NULL);
    } else {
        free(hash->dtah_hash);

        for (h = hash->dtah_all; h != NULL; h = next) {
            next = h->dtahe_nextall;

            aggdata = &h->dtahe_data;

            if (aggdata->dtada_percpu != NULL) {
                for (i = 0; i < max_cpus; i++)
                    free(aggdata->dtada_percpu[i]);
                free(aggdata->dtada_percpu);
            }

            free(aggdata->dtada_data);
            free(h);
        }

        hash->dtah_hash = NULL;
        hash->dtah_all = NULL;
        hash->dtah_size = 0;
        hash->dtah_nent = 0;
    }

    free(agp->dtat_buf.dtbd_data);
    free(agp->dtat_cpus);
}