mp_region.c revision 1
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * See the file LICENSE for redistribution information.
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * Copyright (c) 1996, 1997, 1998
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * Sleepycat Software. All rights reserved.
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlfstatic const char sccsid[] = "@(#)mp_region.c 10.35 (Sleepycat) 12/11/98";
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf#endif /* not lint */
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * __memp_reg_alloc --
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * Allocate some space in the mpool region, with locking.
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * PUBLIC: int __memp_reg_alloc __P((DB_MPOOL *, size_t, size_t *, void *));
f76ee27a7c2e4dbe22aec6ce187c04e980f90349pawelw * __memp_alloc --
f76ee27a7c2e4dbe22aec6ce187c04e980f90349pawelw * Allocate some space in the mpool region.
7a1efdfee8cbdecea34d3d866bbfb46e39b06e0apawelw * PUBLIC: int __memp_alloc __P((DB_MPOOL *, size_t, size_t *, void *));
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlfalloc: if ((ret = __db_shalloc(dbmp->addr, len, MUTEX_ALIGNMENT, &p)) == 0) {
7a70ede882eacbae00c8d5209afb443e7755684cpawelw *(void **)retp = p;
7a70ede882eacbae00c8d5209afb443e7755684cpawelw return (0);
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf "Unable to allocate %lu bytes from mpool shared region: %s\n",
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf /* Look for a buffer on the free list that's the right size. */
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf SH_TAILQ_FIRST(&mp->bhfq, __bh); bhp != NULL; bhp = nbhp) {
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf return (0);
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf /* Discard from the free list until we've freed enough memory. */
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf SH_TAILQ_FIRST(&mp->bhfq, __bh); bhp != NULL; bhp = nbhp) {
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * Retry as soon as we've freed up sufficient space. If we
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * will have to coalesce memory to satisfy the request, don't
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * try until it's likely (possible?) that we'll succeed.
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf SH_TAILQ_FIRST(&mp->bhq, __bh); bhp != NULL; bhp = nbhp) {
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf /* Ignore pinned or locked (I/O in progress) buffers. */
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf /* Find the associated MPOOLFILE. */
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * Write the page if it's dirty.
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * If we wrote the page, fall through and free the buffer. We
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * don't have to rewalk the list to acquire the buffer because
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * it was never available for any other process to modify it.
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * If we didn't write the page, but we discarded and reacquired
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * the region lock, restart the buffer list walk. If we neither
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * wrote the buffer nor discarded the region lock, continue down
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * the buffer list.
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * It's possible that another process wants this buffer
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * and incremented the ref count while we were writing
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * Check to see if the buffer is the size we're looking for.
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * If it is, simply reuse it.
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf return (0);
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf /* Free the buffer. */
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * Retry as soon as we've freed up sufficient space. If we
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * have to coalesce of memory to satisfy the request, don't
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * try until it's likely (possible?) that we'll succeed.
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf /* Restart the walk if we discarded the region lock. */
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * __memp_ropen --
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * Attach to, and optionally create, the mpool region.
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * PUBLIC: int __memp_ropen
2c9565cfcd87a2045c2e4b76f31ac4e978903589ls * PUBLIC: __P((DB_MPOOL *, const char *, size_t, int, int, u_int32_t));
c03acfcad7780db4ddf763511a82026680b3b2c1ls__memp_ropen(dbmp, path, cachesize, mode, is_private, flags)
c03acfcad7780db4ddf763511a82026680b3b2c1ls const char *path;
c03acfcad7780db4ddf763511a82026680b3b2c1ls * Unlike other DB subsystems, mpool can't simply grow the region
c03acfcad7780db4ddf763511a82026680b3b2c1ls * because it returns pointers into the region to its clients. To
c03acfcad7780db4ddf763511a82026680b3b2c1ls * "grow" the region, we'd have to allocate a new region and then
c03acfcad7780db4ddf763511a82026680b3b2c1ls * store a region number in the structures that reference regional
c03acfcad7780db4ddf763511a82026680b3b2c1ls * objects. It's reasonable that we fail regardless, as clients
c03acfcad7780db4ddf763511a82026680b3b2c1ls * shouldn't have every page in the region pinned, so the only
c03acfcad7780db4ddf763511a82026680b3b2c1ls * "failure" mode should be a performance penalty because we don't
c03acfcad7780db4ddf763511a82026680b3b2c1ls * find a page in the cache that we'd like to have found.
c03acfcad7780db4ddf763511a82026680b3b2c1ls * Up the user's cachesize by 25% to account for our overhead.
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf if (cachesize == 0) {
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * Map in the region.
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * If it's a private mpool, use malloc, it's a lot faster than
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * instantiating a region.
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf if ((ret = __os_strdup(path, &dbmp->reginfo.path)) != 0)
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * If we're creating a temporary region, don't use any standard
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * The MPOOL structure is first in the region, the rest of the region
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * is free space.
7a70ede882eacbae00c8d5209afb443e7755684cpawelw /* Initialize a created region. */
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * Assume we want to keep the hash chains with under 10 pages
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * on each chain. We don't know the pagesize in advance, and
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * it may differ for different files. Use a pagesize of 1K for
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * the calculation -- we walk these chains a lot, they should
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf * be short.
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf /* Allocate hash table space and initialize it. */
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf /* Get the local hash table address. */
66f9d5cb3cc0652e2d9d1366fb950efbe4ca2f24mlf return (0);