usr/src/lib/libc/db/mpool/mpool.c

/*-
 * Copyright (c) 1990, 1993
 *      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     8.2 (Berkeley) 2/21/94";
#endif /* LIBC_SCCS and not lint */

#include <sys/param.h>
#include <sys/stat.h>

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <db.h>
#define __MPOOLINTERFACE_PRIVATE
#include "mpool.h"

static BKT *mpool_bkt __P((MPOOL *));
static BKT *mpool_look __P((MPOOL *, pgno_t));
static int  mpool_write __P((MPOOL *, BKT *));
#ifdef DEBUG
static void __mpoolerr __P((const char *fmt, ...));
#endif

/*
 * MPOOL_OPEN -- initialize a memory pool.
 *
 * Parameters:
 *      key:            Shared buffer key.
 *      fd:             File descriptor.
 *      pagesize:       File page size.
 *      maxcache:       Max number of cached pages.
 *
 * Returns:
 *      MPOOL pointer, NULL on error.
 */
MPOOL *
mpool_open(key, fd, pagesize, maxcache)
        DBT *key;
        int fd;
        pgno_t pagesize, maxcache;
{
        struct stat sb;
        MPOOL *mp;
        int entry;

        if (fstat(fd, &sb))
                return (NULL);
        /* XXX
         * We should only set st_size to 0 for pipes -- 4.4BSD has the fix so
         * that stat(2) returns true for ISSOCK on pipes.  Until then, this is
         * fairly close.
         */
        if (!S_ISREG(sb.st_mode)) {
                errno = ESPIPE;
                return (NULL);
        }

        if ((mp = (MPOOL *)malloc(sizeof(MPOOL))) == NULL)
                return (NULL);
        mp->free.cnext = mp->free.cprev = (BKT *)&mp->free;
        mp->lru.cnext = mp->lru.cprev = (BKT *)&mp->lru;
        for (entry = 0; entry < HASHSIZE; ++entry)
                mp->hashtable[entry].hnext = mp->hashtable[entry].hprev =
                    mp->hashtable[entry].cnext = mp->hashtable[entry].cprev =
                    (BKT *)&mp->hashtable[entry];
        mp->curcache = 0;
        mp->maxcache = maxcache;
        mp->pagesize = pagesize;
        mp->npages = sb.st_size / pagesize;
        mp->fd = fd;
        mp->pgcookie = NULL;
        mp->pgin = mp->pgout = NULL;

#ifdef STATISTICS
        mp->cachehit = mp->cachemiss = mp->pagealloc = mp->pageflush =
            mp->pageget = mp->pagenew = mp->pageput = mp->pageread =
            mp->pagewrite = 0;
#endif
        return (mp);
}

/*
 * MPOOL_FILTER -- initialize input/output filters.
 *
 * Parameters:
 *      pgin:           Page in conversion routine.
 *      pgout:          Page out conversion routine.
 *      pgcookie:       Cookie for page in/out routines.
 */
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
 *
 * Parameters:
 *      mp:             mpool cookie
 *      pgnoadddr:      place to store new page number
 * Returns:
 *      RET_ERROR, RET_SUCCESS
 */
void *
mpool_new(mp, pgnoaddr)
        MPOOL *mp;
        pgno_t *pgnoaddr;
{
        BKT *b;
        BKTHDR *hp;

#ifdef STATISTICS
        ++mp->pagenew;
#endif
        /*
         * Get a BKT from the cache.  Assign a new page number, attach it to
         * the hash and lru chains and return.
         */
        if ((b = mpool_bkt(mp)) == NULL)
                return (NULL);
        *pgnoaddr = b->pgno = mp->npages++;
        b->flags = MPOOL_PINNED;
        inshash(b, b->pgno);
        inschain(b, &mp->lru);
        return (b->page);
}

/*
 * MPOOL_GET -- get a page from the pool
 *
 * Parameters:
 *      mp:     mpool cookie
 *      pgno:   page number
 *      flags:  not used
 *
 * Returns:
 *      RET_ERROR, RET_SUCCESS
 */
void *
mpool_get(mp, pgno, flags)
        MPOOL *mp;
        pgno_t pgno;
        u_int flags;            /* XXX not used? */
{
        BKT *b;
        BKTHDR *hp;
        off_t off;
        int nr;

        /*
         * If asking for a specific page that is already in the cache, find
         * it and return it.
         */
        if (b = mpool_look(mp, pgno)) {
#ifdef STATISTICS
                ++mp->pageget;
#endif
#ifdef DEBUG
                if (b->flags & MPOOL_PINNED)
                        __mpoolerr("mpool_get: page %d already pinned",
                            b->pgno);
#endif
                rmchain(b);
                inschain(b, &mp->lru);
                b->flags |= MPOOL_PINNED;
                return (b->page);
        }

        /* Not allowed to retrieve a non-existent page. */
        if (pgno >= mp->npages) {
                errno = EINVAL;
                return (NULL);
        }

        /* Get a page from the cache. */
        if ((b = mpool_bkt(mp)) == NULL)
                return (NULL);
        b->pgno = pgno;
        b->flags = MPOOL_PINNED;

#ifdef STATISTICS
        ++mp->pageread;
#endif
        /* Read in the contents. */
        off = mp->pagesize * pgno;
        if (lseek(mp->fd, off, SEEK_SET) != off)
                return (NULL);
        if ((nr = read(mp->fd, b->page, mp->pagesize)) != mp->pagesize) {
                if (nr >= 0)
                        errno = EFTYPE;
                return (NULL);
        }
        if (mp->pgin)
                (mp->pgin)(mp->pgcookie, b->pgno, b->page);

        inshash(b, b->pgno);
        inschain(b, &mp->lru);
#ifdef STATISTICS
        ++mp->pageget;
#endif
        return (b->page);
}

/*
 * MPOOL_PUT -- return a page to the pool
 *
 * Parameters:
 *      mp:     mpool cookie
 *      page:   page pointer
 *      pgno:   page number
 *
 * Returns:
 *      RET_ERROR, RET_SUCCESS
 */
int
mpool_put(mp, page, flags)
        MPOOL *mp;
        void *page;
        u_int flags;
{
        BKT *baddr;
#ifdef DEBUG
        BKT *b;
#endif

#ifdef STATISTICS
        ++mp->pageput;
#endif
        baddr = (BKT *)((char *)page - sizeof(BKT));
#ifdef DEBUG
        if (!(baddr->flags & MPOOL_PINNED))
                __mpoolerr("mpool_put: page %d not pinned", b->pgno);
        for (b = mp->lru.cnext; b != (BKT *)&mp->lru; b = b->cnext) {
                if (b == (BKT *)&mp->lru)
                        __mpoolerr("mpool_put: %0x: bad address", baddr);
                if (b == baddr)
                        break;
        }
#endif
        baddr->flags &= ~MPOOL_PINNED;
        baddr->flags |= flags & MPOOL_DIRTY;
        return (RET_SUCCESS);
}

/*
 * MPOOL_CLOSE -- close the buffer pool
 *
 * Parameters:
 *      mp:     mpool cookie
 *
 * Returns:
 *      RET_ERROR, RET_SUCCESS
 */
int
mpool_close(mp)
        MPOOL *mp;
{
        BKT *b, *next;

        /* Free up any space allocated to the lru pages. */
        for (b = mp->lru.cprev; b != (BKT *)&mp->lru; b = next) {
                next = b->cprev;
                free(b);
        }
        free(mp);
        return (RET_SUCCESS);
}

/*
 * MPOOL_SYNC -- sync the file to disk.
 *
 * Parameters:
 *      mp:     mpool cookie
 *
 * Returns:
 *      RET_ERROR, RET_SUCCESS
 */
int
mpool_sync(mp)
        MPOOL *mp;
{
        BKT *b;

        for (b = mp->lru.cprev; b != (BKT *)&mp->lru; b = b->cprev)
                if (b->flags & MPOOL_DIRTY && mpool_write(mp, b) == RET_ERROR)
                        return (RET_ERROR);
        return (fsync(mp->fd) ? RET_ERROR : RET_SUCCESS);
}

/*
 * MPOOL_BKT -- get/create a BKT from the cache
 *
 * Parameters:
 *      mp:     mpool cookie
 *
 * Returns:
 *      NULL on failure and a pointer to the BKT on success
 */
static BKT *
mpool_bkt(mp)
        MPOOL *mp;
{
        BKT *b;

        if (mp->curcache < mp->maxcache)
                goto new;

        /*
         * If the cache is maxxed out, search 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 (b = mp->lru.cprev; b != (BKT *)&mp->lru; b = b->cprev)
                if (!(b->flags & MPOOL_PINNED)) {
                        if (b->flags & MPOOL_DIRTY &&
                            mpool_write(mp, b) == RET_ERROR)
                                return (NULL);
                        rmhash(b);
                        rmchain(b);
#ifdef STATISTICS
                        ++mp->pageflush;
#endif
#ifdef DEBUG
                        {
                                void *spage;
                                spage = b->page;
                                memset(b, 0xff, sizeof(BKT) + mp->pagesize);
                                b->page = spage;
                        }
#endif
                        return (b);
                }

new:    if ((b = (BKT *)malloc(sizeof(BKT) + mp->pagesize)) == NULL)
                return (NULL);
#ifdef STATISTICS
        ++mp->pagealloc;
#endif
#ifdef DEBUG
        memset(b, 0xff, sizeof(BKT) + mp->pagesize);
#endif
        b->page = (char *)b + sizeof(BKT);
        ++mp->curcache;
        return (b);
}

/*
 * MPOOL_WRITE -- sync a page to disk
 *
 * Parameters:
 *      mp:     mpool cookie
 *
 * Returns:
 *      RET_ERROR, RET_SUCCESS
 */
static int
mpool_write(mp, b)
        MPOOL *mp;
        BKT *b;
{
        off_t off;

        if (mp->pgout)
                (mp->pgout)(mp->pgcookie, b->pgno, b->page);

#ifdef STATISTICS
        ++mp->pagewrite;
#endif
        off = mp->pagesize * b->pgno;
        if (lseek(mp->fd, off, SEEK_SET) != off)
                return (RET_ERROR);
        if (write(mp->fd, b->page, mp->pagesize) != mp->pagesize)
                return (RET_ERROR);
        b->flags &= ~MPOOL_DIRTY;
        return (RET_SUCCESS);
}

/*
 * MPOOL_LOOK -- lookup a page
 *
 * Parameters:
 *      mp:     mpool cookie
 *      pgno:   page number
 *
 * Returns:
 *      NULL on failure and a pointer to the BKT on success
 */
static BKT *
mpool_look(mp, pgno)
        MPOOL *mp;
        pgno_t pgno;
{
        register BKT *b;
        register BKTHDR *tb;

        /* XXX
         * If find the buffer, put it first on the hash chain so can
         * find it again quickly.
         */
        tb = &mp->hashtable[HASHKEY(pgno)];
        for (b = tb->hnext; b != (BKT *)tb; b = b->hnext)
                if (b->pgno == pgno) {
#ifdef STATISTICS
                        ++mp->cachehit;
#endif
                        return (b);
                }
#ifdef STATISTICS
        ++mp->cachemiss;
#endif
        return (NULL);
}

#ifdef STATISTICS
/*
 * MPOOL_STAT -- cache statistics
 *
 * Parameters:
 *      mp:     mpool cookie
 */
void
mpool_stat(mp)
        MPOOL *mp;
{
        BKT *b;
        int cnt;
        char *sep;

        (void)fprintf(stderr, "%lu pages in the file\n", mp->npages);
        (void)fprintf(stderr,
            "page size %lu, cacheing %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 (b = mp->lru.cnext; b != (BKT *)&mp->lru; b = b->cnext) {
                (void)fprintf(stderr, "%s%d", sep, b->pgno);
                if (b->flags & MPOOL_DIRTY)
                        (void)fprintf(stderr, "d");
                if (b->flags & MPOOL_PINNED)
                        (void)fprintf(stderr, "P");
                if (++cnt == 10) {
                        sep = "\n";
                        cnt = 0;
                } else
                        sep = ", ";

        }
        (void)fprintf(stderr, "\n");
}
#endif

#ifdef DEBUG
#if __STDC__
#include <stdarg.h>
#else
#include <varargs.h>
#endif

static void
#if __STDC__
__mpoolerr(const char *fmt, ...)
#else
__mpoolerr(fmt, va_alist)
        char *fmt;
        va_dcl
#endif
{
        va_list ap;
#if __STDC__
        va_start(ap, fmt);
#else
        va_start(ap);
#endif
        (void)vfprintf(stderr, fmt, ap);
        va_end(ap);
        (void)fprintf(stderr, "\n");
        abort();
        /* NOTREACHED */
}
#endif