/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1996, 1997, 1998
 *      Sleepycat Software.  All rights reserved.
 */
#include "config.h"

#ifndef lint
static const char sccsid[] = "@(#)mp_region.c   10.35 (Sleepycat) 12/11/98";
#endif /* not lint */

#ifndef NO_SYSTEM_INCLUDES
#include <sys/types.h>

#include <errno.h>
#include <string.h>
#endif

#include "db_int.h"
#include "shqueue.h"
#include "db_shash.h"
#include "mp.h"
#include "common_ext.h"

/*
 * __memp_reg_alloc --
 *      Allocate some space in the mpool region, with locking.
 *
 * PUBLIC: int __memp_reg_alloc __P((DB_MPOOL *, size_t, size_t *, void *));
 */
int
__memp_reg_alloc(dbmp, len, offsetp, retp)
        DB_MPOOL *dbmp;
        size_t len, *offsetp;
        void *retp;
{
        int ret;

        LOCKREGION(dbmp);
        ret = __memp_alloc(dbmp, len, offsetp, retp);
        UNLOCKREGION(dbmp);
        return (ret);
}

/*
 * __memp_alloc --
 *      Allocate some space in the mpool region.
 *
 * PUBLIC: int __memp_alloc __P((DB_MPOOL *, size_t, size_t *, void *));
 */
int
__memp_alloc(dbmp, len, offsetp, retp)
        DB_MPOOL *dbmp;
        size_t len, *offsetp;
        void *retp;
{
        BH *bhp, *nbhp;
        MPOOL *mp;
        MPOOLFILE *mfp;
        size_t fsize, total;
        int nomore, restart, ret, wrote;
        void *p;

        mp = dbmp->mp;

        nomore = 0;
alloc:  if ((ret = __db_shalloc(dbmp->addr, len, MUTEX_ALIGNMENT, &p)) == 0) {
                if (offsetp != NULL)
                        *offsetp = R_OFFSET(dbmp, 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, strerror(ret));
                return (ret);
        }

        /* Look for a buffer on the free list that's the right size. */
        for (bhp =
            SH_TAILQ_FIRST(&mp->bhfq, __bh); bhp != NULL; bhp = nbhp) {
                nbhp = SH_TAILQ_NEXT(bhp, q, __bh);

                if (__db_shsizeof(bhp) == len) {
                        SH_TAILQ_REMOVE(&mp->bhfq, bhp, q, __bh);
                        if (offsetp != NULL)
                                *offsetp = R_OFFSET(dbmp, bhp);
                        *(void **)retp = bhp;
                        return (0);
                }
        }

        /* Discard from the free list until we've freed enough memory. */
        total = 0;
        for (bhp =
            SH_TAILQ_FIRST(&mp->bhfq, __bh); bhp != NULL; bhp = nbhp) {
                nbhp = SH_TAILQ_NEXT(bhp, q, __bh);

                SH_TAILQ_REMOVE(&mp->bhfq, bhp, q, __bh);
                __db_shalloc_free(dbmp->addr, bhp);
                --mp->stat.st_page_clean;

                /*
                 * Retry as soon as we've freed up sufficient space.  If we
                 * will have to coalesce memory to satisfy the request, don't
                 * try until it's likely (possible?) that we'll succeed.
                 */
                total += fsize = __db_shsizeof(bhp);
                if (fsize >= len || total >= 3 * len)
                        goto alloc;
        }

retry:  /* Find a buffer we can flush; pure LRU. */
        restart = total = 0;
        for (bhp =
            SH_TAILQ_FIRST(&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. */
                mfp = R_ADDR(dbmp, bhp->mf_offset);

                /*
                 * Write the page if it's dirty.
                 *
                 * If we wrote the page, fall through 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 buffer list walk.  If we neither
                 * wrote the buffer nor discarded the region lock, continue down
                 * the buffer list.
                 */
                if (F_ISSET(bhp, BH_DIRTY)) {
                        ++bhp->ref;
                        if ((ret = __memp_bhwrite(dbmp,
                            mfp, bhp, &restart, &wrote)) != 0)
                                return (ret);
                        --bhp->ref;

                        /*
                         * It's possible that another process wants this buffer
                         * and incremented the ref count while we were writing
                         * it.
                         */
                        if (bhp->ref != 0)
                                goto retry;

                        if (wrote)
                                ++mp->stat.st_rw_evict;
                        else {
                                if (restart)
                                        goto retry;
                                continue;
                        }
                } else
                        ++mp->stat.st_ro_evict;

                /*
                 * Check to see if the buffer is the size we're looking for.
                 * If it is, simply reuse it.
                 */
                total += fsize = __db_shsizeof(bhp);
                if (fsize == len) {
                        __memp_bhfree(dbmp, mfp, bhp, 0);

                        if (offsetp != NULL)
                                *offsetp = R_OFFSET(dbmp, bhp);
                        *(void **)retp = bhp;
                        return (0);
                }

                /* Free the buffer. */
                __memp_bhfree(dbmp, mfp, 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 (fsize >= len || total >= 3 * len)
                        goto alloc;

                /* Restart the walk if we discarded the region lock. */
                if (restart)
                        goto retry;
        }
        nomore = 1;
        goto alloc;
}

/*
 * __memp_ropen --
 *      Attach to, and optionally create, the mpool region.
 *
 * PUBLIC: int __memp_ropen
 * PUBLIC:    __P((DB_MPOOL *, const char *, size_t, int, int, u_int32_t));
 */
int
__memp_ropen(dbmp, path, cachesize, mode, is_private, flags)
        DB_MPOOL *dbmp;
        const char *path;
        size_t cachesize;
        int mode, is_private;
        u_int32_t flags;
{
        MPOOL *mp;
        size_t rlen;
        int defcache, ret;

        /*
         * Unlike other DB subsystems, mpool can't simply grow the region
         * because it returns pointers into the region to its clients.  To
         * "grow" the region, we'd have to allocate a new region and then
         * store a region number in the structures that reference regional
         * objects.  It's reasonable that we fail regardless, as clients
         * shouldn't have every page in the region pinned, so the only
         * "failure" mode should be a performance penalty because we don't
         * find a page in the cache that we'd like to have found.
         *
         * Up the user's cachesize by 25% to account for our overhead.
         */
        defcache = 0;
        if (cachesize < DB_CACHESIZE_MIN)
                if (cachesize == 0) {
                        defcache = 1;
                        cachesize = DB_CACHESIZE_DEF;
                } else
                        cachesize = DB_CACHESIZE_MIN;
        rlen = cachesize + cachesize / 4;

        /*
         * Map in the region.
         *
         * If it's a private mpool, use malloc, it's a lot faster than
         * instantiating a region.
         */
        dbmp->reginfo.dbenv = dbmp->dbenv;
        dbmp->reginfo.appname = DB_APP_NONE;
        if (path == NULL)
                dbmp->reginfo.path = NULL;
        else
                if ((ret = __os_strdup(path, &dbmp->reginfo.path)) != 0)
                        return (ret);
        dbmp->reginfo.file = DB_DEFAULT_MPOOL_FILE;
        dbmp->reginfo.mode = mode;
        dbmp->reginfo.size = rlen;
        dbmp->reginfo.dbflags = flags;
        dbmp->reginfo.flags = 0;
        if (defcache)
                F_SET(&dbmp->reginfo, REGION_SIZEDEF);

        /*
         * If we're creating a temporary region, don't use any standard
         * naming.
         */
        if (is_private) {
                dbmp->reginfo.appname = DB_APP_TMP;
                dbmp->reginfo.file = NULL;
                F_SET(&dbmp->reginfo, REGION_PRIVATE);
        }

        if ((ret = __db_rattach(&dbmp->reginfo)) != 0) {
                if (dbmp->reginfo.path != NULL)
                        __os_freestr(dbmp->reginfo.path);
                return (ret);
        }

        /*
         * The MPOOL structure is first in the region, the rest of the region
         * is free space.
         */
        dbmp->mp = dbmp->reginfo.addr;
        dbmp->addr = (u_int8_t *)dbmp->mp + sizeof(MPOOL);

        /* Initialize a created region. */
        if (F_ISSET(&dbmp->reginfo, REGION_CREATED)) {
                mp = dbmp->mp;
                SH_TAILQ_INIT(&mp->bhq);
                SH_TAILQ_INIT(&mp->bhfq);
                SH_TAILQ_INIT(&mp->mpfq);

                __db_shalloc_init(dbmp->addr, rlen - sizeof(MPOOL));

                /*
                 * Assume we want to keep the hash chains with under 10 pages
                 * on each chain.  We don't know the pagesize in advance, and
                 * it may differ for different files.  Use a pagesize of 1K for
                 * the calculation -- we walk these chains a lot, they should
                 * be short.
                 */
                mp->htab_buckets =
                    __db_tablesize((cachesize / (1 * 1024)) / 10);

                /* Allocate hash table space and initialize it. */
                if ((ret = __db_shalloc(dbmp->addr,
                    mp->htab_buckets * sizeof(DB_HASHTAB),
                    0, &dbmp->htab)) != 0)
                        goto err;
                __db_hashinit(dbmp->htab, mp->htab_buckets);
                mp->htab = R_OFFSET(dbmp, dbmp->htab);

                ZERO_LSN(mp->lsn);
                mp->lsn_cnt = 0;

                memset(&mp->stat, 0, sizeof(mp->stat));
                mp->stat.st_cachesize = cachesize;

                mp->flags = 0;
        }

        /* Get the local hash table address. */
        dbmp->htab = R_ADDR(dbmp, dbmp->mp->htab);

        UNLOCKREGION(dbmp);
        return (0);

err:    UNLOCKREGION(dbmp);
        (void)__db_rdetach(&dbmp->reginfo);
        if (F_ISSET(&dbmp->reginfo, REGION_CREATED))
                (void)memp_unlink(path, 1, dbmp->dbenv);

        if (dbmp->reginfo.path != NULL)
                __os_freestr(dbmp->reginfo.path);
        return (ret);
}