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, 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 (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