263 lines
7.3 KiB
C
263 lines
7.3 KiB
C
/*-
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* Copyright (c) 1998 Michael Smith <msmith@freebsd.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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/*
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* Simple LRU block cache
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*/
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#include <stand.h>
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#include <string.h>
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#include <bitstring.h>
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#include "bootstrap.h"
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/* #define BCACHE_DEBUG */
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#ifdef BCACHE_DEBUG
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#define BCACHE_TIMEOUT 10
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# define DEBUG(fmt, args...) printf("%s: " fmt "\n" , __FUNCTION__ , ## args)
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#else
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#define BCACHE_TIMEOUT 2
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# define DEBUG(fmt, args...)
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#endif
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struct bcachectl
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{
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daddr_t bc_blkno;
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time_t bc_stamp;
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int bc_count;
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};
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static struct bcachectl *bcache_ctl;
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static caddr_t bcache_data;
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static bitstr_t *bcache_miss;
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static int bcache_nblks;
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static int bcache_blksize;
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static int bcache_hits, bcache_misses, bcache_ops, bcache_bypasses;
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static int bcache_bcount;
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static void bcache_insert(caddr_t buf, daddr_t blkno);
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static int bcache_lookup(caddr_t buf, daddr_t blkno);
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/*
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* Initialise the cache for (nblks) of (bsize).
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*/
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int
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bcache_init(int nblks, size_t bsize)
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{
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int i;
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/* discard any old contents */
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if (bcache_data != NULL) {
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free(bcache_data);
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bcache_data = NULL;
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free(bcache_ctl);
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}
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/* Allocate control structures */
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bcache_nblks = nblks;
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bcache_blksize = bsize;
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bcache_data = malloc(bcache_nblks * bcache_blksize);
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bcache_ctl = (struct bcachectl *)malloc(bcache_nblks * sizeof(struct bcachectl));
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bcache_miss = bit_alloc((bcache_nblks + 1) / 2);
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if ((bcache_data == NULL) || (bcache_ctl == NULL) || (bcache_miss == NULL)) {
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if (bcache_miss)
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free(bcache_miss);
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if (bcache_ctl)
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free(bcache_ctl);
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if (bcache_data)
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free(bcache_data);
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bcache_data = NULL;
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return(ENOMEM);
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}
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/* Invalidate the cache */
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for (i = 0; i < bcache_nblks; i++) {
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bcache_ctl[i].bc_count = -1;
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bcache_ctl[i].bc_blkno = -1;
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}
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return(0);
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}
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/*
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* Handle a transfer request; fill in parts of the request that can
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* be satisfied by the cache, use the supplied strategy routine to do
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* device I/O and then use the I/O results to populate the cache.
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*
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* Requests larger than 1/2 the cache size will be bypassed and go
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* directly to the disk. XXX tune this.
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*/
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int
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bcache_strategy(void *devdata, int rw, daddr_t blk, size_t size, void *buf, size_t *rsize)
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{
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struct bcache_devdata *dd = (struct bcache_devdata *)devdata;
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int nblk, p_size;
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daddr_t p_blk;
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caddr_t p_buf;
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int i, j, result;
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bcache_ops++;
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/* bypass large requests, or when the cache is inactive */
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if ((bcache_data == NULL) || ((size * 2 / bcache_blksize) > bcache_nblks)) {
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DEBUG("bypass %d from %d", size / bcache_blksize, blk);
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bcache_bypasses++;
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return(dd->dv_strategy(dd->dv_devdata, rw, blk, size, buf, rsize));
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}
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nblk = size / bcache_blksize;
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result = 0;
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/* Satisfy any cache hits up front */
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for (i = 0; i < nblk; i++) {
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if (bcache_lookup(buf + (bcache_blksize * i), blk + i)) {
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bit_set(bcache_miss, i); /* cache miss */
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bcache_misses++;
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} else {
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bit_clear(bcache_miss, i); /* cache hit */
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bcache_hits++;
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}
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}
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/* Go back and fill in any misses XXX optimise */
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p_blk = -1;
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p_buf = NULL;
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p_size = 0;
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for (i = 0; i < nblk; i++) {
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if (bit_test(bcache_miss, i)) {
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/* miss, add to pending transfer */
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if (p_blk == -1) {
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p_blk = blk + i;
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p_buf = buf + (bcache_blksize * i);
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p_size = 1;
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} else {
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p_size++;
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}
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} else if (p_blk != -1) {
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/* hit, complete pending transfer */
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result = dd->dv_strategy(dd->dv_devdata, rw, p_blk, p_size * bcache_blksize, p_buf, NULL);
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if (result != 0)
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goto done;
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for (j = 0; j < p_size; j++)
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bcache_insert(p_buf + (j * bcache_blksize), p_blk + j);
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p_blk = -1;
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}
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}
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if (p_blk != -1) {
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/* pending transfer left */
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result = dd->dv_strategy(dd->dv_devdata, rw, p_blk, p_size * bcache_blksize, p_buf, NULL);
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if (result != 0)
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goto done;
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for (j = 0; j < p_size; j++)
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bcache_insert(p_buf + (j * bcache_blksize), p_blk + j);
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}
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done:
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if ((result == 0) && (rsize != NULL))
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*rsize = size;
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return(result);
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}
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/*
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* Insert a block into the cache. Retire the oldest block to do so, if required.
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*
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* XXX the LRU algorithm will fail after 2^31 blocks have been transferred.
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*/
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static void
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bcache_insert(caddr_t buf, daddr_t blkno)
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{
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time_t now;
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int i, cand, ocount;
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time(&now);
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cand = 0; /* assume the first block */
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ocount = bcache_ctl[0].bc_count;
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/* find the oldest block */
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for (i = 1; i < bcache_nblks; i++) {
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if (bcache_ctl[i].bc_blkno == blkno) {
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/* reuse old entry */
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cand = i;
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break;
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}
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if (bcache_ctl[i].bc_count < ocount) {
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ocount = bcache_ctl[i].bc_count;
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cand = i;
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}
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}
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DEBUG("insert blk %d -> %d @ %d # %d", blkno, cand, now, bcache_bcount);
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bcopy(buf, bcache_data + (bcache_blksize * cand), bcache_blksize);
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bcache_ctl[cand].bc_blkno = blkno;
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bcache_ctl[cand].bc_stamp = now;
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bcache_ctl[cand].bc_count = bcache_bcount++;
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}
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/*
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* Look for a block in the cache. Blocks more than BCACHE_TIMEOUT seconds old
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* may be stale (removable media) and thus are discarded. Copy the block out
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* if successful and return zero, or return nonzero on failure.
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*/
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static int
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bcache_lookup(caddr_t buf, daddr_t blkno)
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{
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time_t now;
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int i;
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time(&now);
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for (i = 0; i < bcache_nblks; i++)
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/* cache hit? */
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if ((bcache_ctl[i].bc_blkno == blkno) && ((bcache_ctl[i].bc_stamp + BCACHE_TIMEOUT) >= now)) {
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bcopy(bcache_data + (bcache_blksize * i), buf, bcache_blksize);
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DEBUG("hit blk %d <- %d (now %d then %d)", blkno, i, now, bcache_ctl[i].bc_stamp);
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return(0);
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}
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return(ENOENT);
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}
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COMMAND_SET(bcachestat, "bcachestat", "get disk block cache stats", command_bcache);
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static int
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command_bcache(int argc, char *argv[])
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{
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int i;
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for (i = 0; i < bcache_nblks; i++) {
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printf("%08x %04x %04x|", bcache_ctl[i].bc_blkno, (unsigned int)bcache_ctl[i].bc_stamp & 0xffff, bcache_ctl[i].bc_count & 0xffff);
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if (((i + 1) % 4) == 0)
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printf("\n");
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}
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printf("\n%d ops %d bypasses %d hits %d misses\n", bcache_ops, bcache_bypasses, bcache_hits, bcache_misses);
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return(CMD_OK);
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}
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