vmem_sbrk.c revision 7257d1b4d25bfac0c802847390e98a464fd787ac
/*
* 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 2008 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
#pragma ident "%Z%%M% %I% %E% SMI"
/*
* The structure of the sbrk backend:
*
* +-----------+
* | sbrk_top |
* +-----------+
* | (vmem_sbrk_alloc(), vmem_free())
* |
* +-----------+
* | sbrk_heap |
* +-----------+
* | | ... | (vmem_alloc(), vmem_free())
* <other arenas>
*
* The sbrk_top arena holds all controlled memory. vmem_sbrk_alloc() handles
* allocations from it, including growing the heap when we run low.
*
* Growing the heap is complicated by the fact that we have to extend the
* sbrk_top arena (using _vmem_extend_alloc()), and that can fail. Since
* other threads may be actively allocating, we can't return the memory.
*
* Instead, we put it on a doubly-linked list, sbrk_fails, which we search
* before calling sbrk().
*/
#include <errno.h>
#include <limits.h>
#include <sys/sysmacros.h>
#include <sys/mman.h>
#include <unistd.h>
#include "vmem_base.h"
#include "misc.h"
size_t vmem_sbrk_pagesize = 0; /* the preferred page size of the heap */
#define VMEM_SBRK_MINALLOC (64 * 1024)
size_t vmem_sbrk_minalloc = VMEM_SBRK_MINALLOC; /* minimum allocation */
static size_t real_pagesize;
static vmem_t *sbrk_heap;
typedef struct sbrk_fail {
struct sbrk_fail *sf_next;
struct sbrk_fail *sf_prev;
void *sf_base; /* == the sbrk_fail's address */
size_t sf_size; /* the size of this buffer */
} sbrk_fail_t;
static sbrk_fail_t sbrk_fails = {
&sbrk_fails,
&sbrk_fails,
NULL,
0
};
static mutex_t sbrk_faillock = DEFAULTMUTEX;
/*
* Try to extend src with [pos, pos + size).
*
* If it fails, add the block to the sbrk_fails list.
*/
static void *
vmem_sbrk_extend_alloc(vmem_t *src, void *pos, size_t size, size_t alloc,
int vmflags)
{
sbrk_fail_t *fnext, *fprev, *fp;
void *ret;
ret = _vmem_extend_alloc(src, pos, size, alloc, vmflags);
if (ret != NULL)
return (ret);
fp = (sbrk_fail_t *)pos;
ASSERT(sizeof (sbrk_fail_t) <= size);
fp->sf_base = pos;
fp->sf_size = size;
(void) mutex_lock(&sbrk_faillock);
fp->sf_next = fnext = &sbrk_fails;
fp->sf_prev = fprev = sbrk_fails.sf_prev;
fnext->sf_prev = fp;
fprev->sf_next = fp;
(void) mutex_unlock(&sbrk_faillock);
return (NULL);
}
/*
* Try to add at least size bytes to src, using the sbrk_fails list
*/
static void *
vmem_sbrk_tryfail(vmem_t *src, size_t size, int vmflags)
{
sbrk_fail_t *fp;
(void) mutex_lock(&sbrk_faillock);
for (fp = sbrk_fails.sf_next; fp != &sbrk_fails; fp = fp->sf_next) {
if (fp->sf_size >= size) {
fp->sf_next->sf_prev = fp->sf_prev;
fp->sf_prev->sf_next = fp->sf_next;
fp->sf_next = fp->sf_prev = NULL;
break;
}
}
(void) mutex_unlock(&sbrk_faillock);
if (fp != &sbrk_fails) {
ASSERT(fp->sf_base == (void *)fp);
return (vmem_sbrk_extend_alloc(src, fp, fp->sf_size, size,
vmflags));
}
/*
* nothing of the right size on the freelist
*/
return (NULL);
}
static void *
vmem_sbrk_alloc(vmem_t *src, size_t size, int vmflags)
{
extern void *_sbrk_grow_aligned(size_t min_size, size_t low_align,
size_t high_align, size_t *actual_size);
void *ret;
void *buf;
size_t buf_size;
int old_errno = errno;
ret = vmem_alloc(src, size, VM_NOSLEEP);
if (ret != NULL) {
errno = old_errno;
return (ret);
}
/*
* The allocation failed. We need to grow the heap.
*
* First, try to use any buffers which failed earlier.
*/
if (sbrk_fails.sf_next != &sbrk_fails &&
(ret = vmem_sbrk_tryfail(src, size, vmflags)) != NULL)
return (ret);
buf_size = MAX(size, vmem_sbrk_minalloc);
/*
* buf_size gets overwritten with the actual allocated size
*/
buf = _sbrk_grow_aligned(buf_size, real_pagesize, vmem_sbrk_pagesize,
&buf_size);
if (buf != MAP_FAILED) {
ret = vmem_sbrk_extend_alloc(src, buf, buf_size, size, vmflags);
if (ret != NULL) {
errno = old_errno;
return (ret);
}
}
/*
* Growing the heap failed. The vmem_alloc() above called umem_reap().
*/
ASSERT((vmflags & VM_NOSLEEP) == VM_NOSLEEP);
errno = old_errno;
return (NULL);
}
/*
* fork1() support
*/
void
vmem_sbrk_lockup(void)
{
(void) mutex_lock(&sbrk_faillock);
}
void
vmem_sbrk_release(void)
{
(void) mutex_unlock(&sbrk_faillock);
}
vmem_t *
vmem_sbrk_arena(vmem_alloc_t **a_out, vmem_free_t **f_out)
{
if (sbrk_heap == NULL) {
size_t heap_size;
real_pagesize = sysconf(_SC_PAGESIZE);
heap_size = vmem_sbrk_pagesize;
if (issetugid()) {
heap_size = 0;
} else if (heap_size != 0 && !ISP2(heap_size)) {
heap_size = 0;
log_message("ignoring bad pagesize: 0x%p\n", heap_size);
}
if (heap_size <= real_pagesize) {
heap_size = real_pagesize;
} else {
struct memcntl_mha mha;
mha.mha_cmd = MHA_MAPSIZE_BSSBRK;
mha.mha_flags = 0;
mha.mha_pagesize = heap_size;
if (memcntl(NULL, 0, MC_HAT_ADVISE, (char *)&mha, 0, 0)
== -1) {
log_message("unable to set MAPSIZE_BSSBRK to "
"0x%p\n", heap_size);
heap_size = real_pagesize;
}
}
vmem_sbrk_pagesize = heap_size;
/* validate vmem_sbrk_minalloc */
if (vmem_sbrk_minalloc < VMEM_SBRK_MINALLOC)
vmem_sbrk_minalloc = VMEM_SBRK_MINALLOC;
vmem_sbrk_minalloc = P2ROUNDUP(vmem_sbrk_minalloc, heap_size);
sbrk_heap = vmem_init("sbrk_top", real_pagesize,
vmem_sbrk_alloc, vmem_free,
"sbrk_heap", NULL, 0, real_pagesize,
vmem_alloc, vmem_free);
}
if (a_out != NULL)
*a_out = vmem_alloc;
if (f_out != NULL)
*f_out = vmem_free;
return (sbrk_heap);
}