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/*-
* See the file LICENSE for redistribution information.
*
* Copyright (c) 1996, 1997, 1998, 1999, 2000
* Sleepycat Software. All rights reserved.
*/
#include "db_config.h"
#ifndef lint
static const char revid[] = "$Id: mp_alloc.c,v 11.7 2000/04/20 21:14:18 bostic Exp $";
#endif /* not lint */
#ifndef NO_SYSTEM_INCLUDES
#include <sys/types.h>
#endif
#include "db_int.h"
#include "db_shash.h"
#include "mp.h"
/*
* __memp_alloc --
* Allocate some space from a cache region.
*
* PUBLIC: int __memp_alloc __P((DB_MPOOL *,
* PUBLIC: REGINFO *, MPOOLFILE *, size_t, roff_t *, void *));
*/
int
__memp_alloc(dbmp, memreg, mfp, len, offsetp, retp)
DB_MPOOL *dbmp;
REGINFO *memreg;
MPOOLFILE *mfp;
size_t len;
roff_t *offsetp;
void *retp;
{
BH *bhp, *nbhp;
MPOOL *c_mp;
MPOOLFILE *bh_mfp;
size_t total;
int nomore, restart, ret, wrote;
void *p;
c_mp = memreg->primary;
/*
* If we're allocating a buffer, and the one we're discarding is the
* same size, we don't want to waste the time to re-integrate it into
* the shared memory free list. If the DB_MPOOLFILE argument isn't
* NULL, we'll compare the underlying page sizes of the two buffers
* before free-ing and re-allocating buffers.
*/
if (mfp != NULL)
len = (sizeof(BH) - sizeof(u_int8_t)) + mfp->stat.st_pagesize;
nomore = 0;
alloc: if ((ret = __db_shalloc(memreg->addr, len, MUTEX_ALIGN, &p)) == 0) {
if (offsetp != NULL)
*offsetp = R_OFFSET(memreg, p);
*(void **)retp = p;
return (0);
}
if (nomore) {
__db_err(dbmp->dbenv,
"Unable to allocate %lu bytes from mpool shared region: %s\n",
(u_long)len, db_strerror(ret));
return (ret);
}
retry: /* Find a buffer we can flush; pure LRU. */
restart = total = 0;
for (bhp =
SH_TAILQ_FIRST(&c_mp->bhq, __bh); bhp != NULL; bhp = nbhp) {
nbhp = SH_TAILQ_NEXT(bhp, q, __bh);
/* Ignore pinned or locked (I/O in progress) buffers. */
if (bhp->ref != 0 || F_ISSET(bhp, BH_LOCKED))
continue;
/* Find the associated MPOOLFILE. */
bh_mfp = R_ADDR(dbmp->reginfo, bhp->mf_offset);
/* Write the page if it's dirty. */
if (F_ISSET(bhp, BH_DIRTY)) {
++bhp->ref;
if ((ret = __memp_bhwrite(dbmp,
bh_mfp, bhp, &restart, &wrote)) != 0)
return (ret);
--bhp->ref;
/*
* Another process may have acquired this buffer and
* incremented the ref count after we wrote it.
*/
if (bhp->ref != 0)
goto retry;
/*
* If we wrote the page, continue and free the buffer.
* We don't have to rewalk the list to acquire the
* buffer because it was never available for any other
* process to modify it.
*
* If we didn't write the page, but we discarded and
* reacquired the region lock, restart the list walk.
*
* If we neither wrote the buffer nor discarded the
* region lock, continue down the buffer list.
*/
if (wrote)
++c_mp->stat.st_rw_evict;
else {
if (restart)
goto retry;
continue;
}
} else
++c_mp->stat.st_ro_evict;
/*
* Check to see if the buffer is the size we're looking for.
* If it is, simply reuse it.
*/
if (mfp != NULL &&
mfp->stat.st_pagesize == bh_mfp->stat.st_pagesize) {
__memp_bhfree(dbmp, bhp, 0);
if (offsetp != NULL)
*offsetp = R_OFFSET(memreg, bhp);
*(void **)retp = bhp;
return (0);
}
/* Note how much space we've freed, and free the buffer. */
total += __db_shsizeof(bhp);
__memp_bhfree(dbmp, bhp, 1);
/*
* Retry as soon as we've freed up sufficient space. If we
* have to coalesce of memory to satisfy the request, don't
* try until it's likely (possible?) that we'll succeed.
*/
if (total >= 3 * len)
goto alloc;
/* Restart the walk if we discarded the region lock. */
if (restart)
goto retry;
}
nomore = 1;
goto alloc;
}
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