mpool.c

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/*-
 * Copyright (c) 1990, 1993, 1994
 *  The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *  This product includes software developed by the University of
 *  California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */
 
#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)mpool.c 8.5 (Berkeley) 7/26/94";
#endif /* LIBC_SCCS and not lint */
 
#include <sys/param.h>
#include <sys/queue.h>
#include <sys/stat.h>
 
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
 
#include "../include/db.h"
 
#define __MPOOLINTERFACE_PRIVATE
#include <mpool.h>
 
#undef __APPLE__
 
#ifndef __APPLE__
#define mpool_open __mpool_open
#define mpool_filter __mpool_filter
#define mpool_new __mpool_new
#define mpool_get __mpool_get
#define mpool_put __mpool_put
#define mpool_sync __mpool_sync
#define mpool_close __mpool_close
#endif
 
static BKT *mpool_bkt __P((MPOOL *));
static BKT *mpool_look __P((MPOOL *, pgno_t));
static int  mpool_write __P((MPOOL *, BKT *));
 
/*
 * mpool_open --
 *  Initialize a memory pool.
 */
MPOOL *
mpool_open(key, fd, pagesize, maxcache)
    void *key;
    int fd;
    pgno_t pagesize, maxcache;
{
    struct stat sb;
    MPOOL *mp;
    int entry;
 
    /*
     * Get information about the file.
     *
     * XXX
     * We don't currently handle pipes, although we should.
     */
    if (fstat(fd, &sb))
        return (NULL);
    if (!S_ISREG(sb.st_mode)) {
        errno = ESPIPE;
        return (NULL);
    }
 
    /* Allocate and initialize the MPOOL cookie. */
    if ((mp = (MPOOL *)calloc(1, sizeof(MPOOL))) == NULL)
        return (NULL);
    CIRCLEQ_INIT(&mp->lqh);
    for (entry = 0; entry < HASHSIZE; ++entry)
        CIRCLEQ_INIT(&mp->hqh[entry]);
    mp->maxcache = maxcache;
    mp->npages = sb.st_size / pagesize;
    mp->pagesize = pagesize;
    mp->fd = fd;
    return (mp);
}
 
/*
 * mpool_filter --
 *  Initialize input/output filters.
 */
void
mpool_filter(mp, pgin, pgout, pgcookie)
    MPOOL *mp;
    void (*pgin) __P((void *, pgno_t, void *));
    void (*pgout) __P((void *, pgno_t, void *));
    void *pgcookie;
{
    mp->pgin = pgin;
    mp->pgout = pgout;
    mp->pgcookie = pgcookie;
}
 
/*
 * mpool_new --
 *  Get a new page of memory.
 */
void *
mpool_new(mp, pgnoaddr)
    MPOOL *mp;
    pgno_t *pgnoaddr;
{
    struct _hqh *head;
    BKT *bp;
 
    if (mp->npages == MAX_PAGE_NUMBER) {
        (void)fprintf(stderr, "mpool_new: page allocation overflow.\n");
        abort();
    }
#ifdef STATISTICS
    ++mp->pagenew;
#endif
    /*
     * Get a BKT from the cache.  Assign a new page number, attach
     * it to the head of the hash chain, the tail of the lru chain,
     * and return.
     */
    if ((bp = mpool_bkt(mp)) == NULL)
        return (NULL);
    *pgnoaddr = bp->pgno = mp->npages++;
    bp->flags = MPOOL_PINNED;
 
    head = &mp->hqh[HASHKEY(bp->pgno)];
    CIRCLEQ_INSERT_HEAD(head, bp, hq);
    CIRCLEQ_INSERT_TAIL(&mp->lqh, bp, q);
    return (bp->page);
}
 
/*
 * mpool_get
 *  Get a page.
 */
void *
mpool_get(mp, pgno, flags)
    MPOOL *mp;
    pgno_t pgno;
    u_int flags;                /* XXX not used? */
{
    struct _hqh *head;
    BKT *bp;
    off_t off;
    int nr;
 
    /* Check for attempt to retrieve a non-existent page. */
    if (pgno >= mp->npages) {
        errno = EINVAL;
        return (NULL);
    }
 
#ifdef STATISTICS
    ++mp->pageget;
#endif
 
    /* Check for a page that is cached. */
    if ((bp = mpool_look(mp, pgno)) != NULL) {
#ifdef DEBUG
        if (bp->flags & MPOOL_PINNED) {
            (void)fprintf(stderr,
                "mpool_get: page %d already pinned\n", bp->pgno);
            abort();
        }
#endif
        /*
         * Move the page to the head of the hash chain and the tail
         * of the lru chain.
         */
        head = &mp->hqh[HASHKEY(bp->pgno)];
        CIRCLEQ_REMOVE(head, bp, hq);
        CIRCLEQ_INSERT_HEAD(head, bp, hq);
        CIRCLEQ_REMOVE(&mp->lqh, bp, q);
        CIRCLEQ_INSERT_TAIL(&mp->lqh, bp, q);
 
        /* Return a pinned page. */
        bp->flags |= MPOOL_PINNED;
        return (bp->page);
    }
 
    /* Get a page from the cache. */
    if ((bp = mpool_bkt(mp)) == NULL)
        return (NULL);
 
    /* Read in the contents. */
#ifdef STATISTICS
    ++mp->pageread;
#endif
    off = mp->pagesize * pgno;
    if (lseek(mp->fd, off, SEEK_SET) != off)
        return (NULL);
    if ((u_long) (nr = read(mp->fd, bp->page, mp->pagesize))
        != mp->pagesize) {
        if (nr >= 0)
            errno = EFTYPE;
        return (NULL);
    }
 
    /* Set the page number, pin the page. */
    bp->pgno = pgno;
    bp->flags = MPOOL_PINNED;
 
    /*
     * Add the page to the head of the hash chain and the tail
     * of the lru chain.
     */
    head = &mp->hqh[HASHKEY(bp->pgno)];
    CIRCLEQ_INSERT_HEAD(head, bp, hq);
    CIRCLEQ_INSERT_TAIL(&mp->lqh, bp, q);
 
    /* Run through the user's filter. */
    if (mp->pgin != NULL)
        (mp->pgin)(mp->pgcookie, bp->pgno, bp->page);
 
    return (bp->page);
}
 
/*
 * mpool_put
 *  Return a page.
 */
int
mpool_put(mp, page, flags)
    MPOOL *mp;
    void *page;
    u_int flags;
{
    BKT *bp;
 
#ifdef STATISTICS
    ++mp->pageput;
#endif
    bp = (BKT *)((char *)page - sizeof(BKT));
#ifdef DEBUG
    if (!(bp->flags & MPOOL_PINNED)) {
        (void)fprintf(stderr,
            "mpool_put: page %d not pinned\n", bp->pgno);
        abort();
    }
#endif
    bp->flags &= ~MPOOL_PINNED;
    bp->flags |= flags & MPOOL_DIRTY;
    return (RET_SUCCESS);
}
 
/*
 * mpool_close
 *  Close the buffer pool.
 */
int
mpool_close(mp)
    MPOOL *mp;
{
    BKT *bp;
 
    /* Free up any space allocated to the lru pages. */
    while ((bp = mp->lqh.cqh_first) != (void *)&mp->lqh) {
        CIRCLEQ_REMOVE(&mp->lqh, mp->lqh.cqh_first, q);
        free(bp);
    }
 
    /* Free the MPOOL cookie. */
    free(mp);
    return (RET_SUCCESS);
}
 
/*
 * mpool_sync
 *  Sync the pool to disk.
 */
int
mpool_sync(mp)
    MPOOL *mp;
{
    BKT *bp;
 
    /* Walk the lru chain, flushing any dirty pages to disk. */
    for (bp = mp->lqh.cqh_first;
        bp != (void *)&mp->lqh; bp = bp->q.cqe_next)
        if (bp->flags & MPOOL_DIRTY &&
            mpool_write(mp, bp) == RET_ERROR)
            return (RET_ERROR);
 
    /* Sync the file descriptor. */
    return (fsync(mp->fd) ? RET_ERROR : RET_SUCCESS);
}
 
#define __APPLE__
 
#ifndef __APPLE__
#undef mpool_open
#undef mpool_filter
#undef mpool_new
#undef mpool_get
#undef mpool_put
#undef mpool_close
#undef mpool_sync
 
#define weak_alias(original, alias) \
    asm (".weak " #alias "\n" #alias " = " #original);
weak_alias (__mpool_open, mpool_open)
weak_alias (__mpool_filter, mpool_filter)
weak_alias (__mpool_new, mpool_new)
weak_alias (__mpool_get, mpool_get)
weak_alias (__mpool_put, mpool_put)
weak_alias (__mpool_close, mpool_close)
weak_alias (__mpool_sync, mpool_sync)
#endif
 
/*
 * mpool_bkt
 *  Get a page from the cache (or create one).
 */
static BKT *
mpool_bkt(mp)
    MPOOL *mp;
{
    struct _hqh *head;
    BKT *bp;
 
    /* If under the max cached, always create a new page. */
    if (mp->curcache < mp->maxcache)
        goto new;
 
    /*
     * If the cache is max'd out, walk the lru list for a buffer we
     * can flush.  If we find one, write it (if necessary) and take it
     * off any lists.  If we don't find anything we grow the cache anyway.
     * The cache never shrinks.
     */
    for (bp = mp->lqh.cqh_first;
        bp != (void *)&mp->lqh; bp = bp->q.cqe_next)
        if (!(bp->flags & MPOOL_PINNED)) {
            /* Flush if dirty. */
            if (bp->flags & MPOOL_DIRTY &&
                mpool_write(mp, bp) == RET_ERROR)
                return (NULL);
#ifdef STATISTICS
            ++mp->pageflush;
#endif
            /* Remove from the hash and lru queues. */
            head = &mp->hqh[HASHKEY(bp->pgno)];
            CIRCLEQ_REMOVE(head, bp, hq);
            CIRCLEQ_REMOVE(&mp->lqh, bp, q);
#ifdef DEBUG
            { void *spage;
                spage = bp->page;
                memset(bp, 0xff, sizeof(BKT) + mp->pagesize);
                bp->page = spage;
            }
#endif
            return (bp);
        }
 
new:    if ((bp = (BKT *) calloc(1, sizeof(BKT) + mp->pagesize)) == NULL)
        return (NULL);
#ifdef STATISTICS
    ++mp->pagealloc;
#endif
#if defined(DEBUG) || defined(PURIFY)
    memset(bp, 0xff, sizeof(BKT) + mp->pagesize);
#endif
    bp->page = (char *)bp + sizeof(BKT);
    ++mp->curcache;
    return (bp);
}
 
/*
 * mpool_write
 *  Write a page to disk.
 */
static int
mpool_write(mp, bp)
    MPOOL *mp;
    BKT *bp;
{
    off_t off;
 
#ifdef STATISTICS
    ++mp->pagewrite;
#endif
 
    /* Run through the user's filter. */
    if (mp->pgout)
        (mp->pgout)(mp->pgcookie, bp->pgno, bp->page);
 
    off = mp->pagesize * bp->pgno;
    if (lseek(mp->fd, off, SEEK_SET) != off)
        return (RET_ERROR);
    if ((u_long) write(mp->fd, bp->page, mp->pagesize) != mp->pagesize)
        return (RET_ERROR);
 
    bp->flags &= ~MPOOL_DIRTY;
    return (RET_SUCCESS);
}
 
/*
 * mpool_look
 *  Lookup a page in the cache.
 */
static BKT *
mpool_look(mp, pgno)
    MPOOL *mp;
    pgno_t pgno;
{
    struct _hqh *head;
    BKT *bp;
 
    head = &mp->hqh[HASHKEY(pgno)];
    for (bp = head->cqh_first; bp != (void *)head; bp = bp->hq.cqe_next)
        if (bp->pgno == pgno) {
#ifdef STATISTICS
            ++mp->cachehit;
#endif
            return (bp);
        }
#ifdef STATISTICS
    ++mp->cachemiss;
#endif
    return (NULL);
}
 
#ifdef STATISTICS
/*
 * mpool_stat
 *  Print out cache statistics.
 */
void
mpool_stat(mp)
    MPOOL *mp;
{
    BKT *bp;
    int cnt;
    char *sep;
 
    (void)fprintf(stderr, "%lu pages in the file\n", mp->npages);
    (void)fprintf(stderr,
        "page size %lu, caching %lu pages of %lu page max cache\n",
        mp->pagesize, mp->curcache, mp->maxcache);
    (void)fprintf(stderr, "%lu page puts, %lu page gets, %lu page new\n",
        mp->pageput, mp->pageget, mp->pagenew);
    (void)fprintf(stderr, "%lu page allocs, %lu page flushes\n",
        mp->pagealloc, mp->pageflush);
    if (mp->cachehit + mp->cachemiss)
        (void)fprintf(stderr,
            "%.0f%% cache hit rate (%lu hits, %lu misses)\n",
            ((double)mp->cachehit / (mp->cachehit + mp->cachemiss))
            * 100, mp->cachehit, mp->cachemiss);
    (void)fprintf(stderr, "%lu page reads, %lu page writes\n",
        mp->pageread, mp->pagewrite);
 
    sep = "";
    cnt = 0;
    for (bp = mp->lqh.cqh_first;
        bp != (void *)&mp->lqh; bp = bp->q.cqe_next) {
        (void)fprintf(stderr, "%s%d", sep, bp->pgno);
        if (bp->flags & MPOOL_DIRTY)
            (void)fprintf(stderr, "d");
        if (bp->flags & MPOOL_PINNED)
            (void)fprintf(stderr, "P");
        if (++cnt == 10) {
            sep = "\n";
            cnt = 0;
        } else
            sep = ", ";
 
    }
    (void)fprintf(stderr, "\n");
}
#endif