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-rw-r--r--db/mpool/mpool.c463
1 files changed, 463 insertions, 0 deletions
diff --git a/db/mpool/mpool.c b/db/mpool/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 <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 *));
+
+/*
+ * 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 ((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);
+}
+
+/*
+ * 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 *)malloc(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 (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