Implement a simple LRU block cache. By default this is initialised to 16k,
and will bypass transfers for more than 8k. Blocks are invalidated after 2 seconds, so removable media should not confuse the cache. The 8k threshold is a compromise; all UFS transfers performed by libstand are 8k or less, so large file reads thrash the cache. However many filesystem metadata operations are also performed using 8k blocks, so using a lower threshold gives poor performance. Those of you with an eye for cache algorithms are welcome to tell me how badly this one sucks; you can start with the 'bcachestats' command which will print the contents of the cache and access statistics.
This commit is contained in:
msmith
parent
773a7664df
commit
c327eb0fef
@ -24,7 +24,7 @@
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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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* $Id: main.c,v 1.7 1998/10/24 00:31:21 msmith Exp $
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* $Id: main.c,v 1.8 1998/10/31 17:12:32 dfr Exp $
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*/
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@ -141,6 +141,11 @@ main(void)
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/* switch to OSF pal code. */
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OSFpal();
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/*
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* Initialise the block cache
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*/
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bcache_init(32, 512); /* 16k XXX tune this */
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/*
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* March through the device switch probing for things.
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*/
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@ -24,7 +24,7 @@
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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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* $Id: srmdisk.c,v 1.1.1.1 1998/08/21 03:17:42 msmith Exp $
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* $Id: srmdisk.c,v 1.2 1998/10/31 17:12:32 dfr Exp $
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*/
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/*
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@ -61,6 +61,7 @@
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static int bd_init(void);
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static int bd_strategy(void *devdata, int flag, daddr_t dblk, size_t size, void *buf, size_t *rsize);
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static int bd_realstrategy(void *devdata, int flag, daddr_t dblk, size_t size, void *buf, size_t *rsize);
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static int bd_open(struct open_file *f, void *vdev);
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static int bd_close(struct open_file *f);
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static void bd_print(int verbose);
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@ -70,10 +71,6 @@ struct open_disk {
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int od_unit; /* our unit number */
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int od_boff; /* block offset from beginning of SRM disk */
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int od_flags;
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#define BD_MODEMASK 0x3
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#define BD_MODEINT13 0x0
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#define BD_MODEEDD1 0x1
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#define BD_MODEEDD3 0x2
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#define BD_FLOPPY (1<<2)
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u_char od_buf[BUFSIZE]; /* transfer buffer (do we want/need this?) */
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};
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@ -326,7 +323,17 @@ bd_close(struct open_file *f)
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}
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static int
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bd_strategy(void *devdata, int flag, daddr_t dblk, size_t size, void *buf, size_t *rsize)
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bd_strategy(void *devdata, int rw, daddr_t dblk, size_t size, void *buf, size_t *rsize)
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{
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struct bcache_devdata bcd;
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bcd.dv_strategy = bd_realstrategy;
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bcd.dv_devdata = devdata;
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return(bcache_strategy(&bcd, rw, dblk, size, buf, rsize));
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}
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static int
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bd_realstrategy(void *devdata, int flag, daddr_t dblk, size_t size, void *buf, size_t *rsize)
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{
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prom_return_t ret;
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struct open_disk *od = (struct open_disk *)devdata;
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@ -1,7 +1,8 @@
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# $Id: Makefile.inc,v 1.5 1998/09/14 18:27:04 msmith Exp $
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# $Id: Makefile.inc,v 1.6 1998/09/30 19:38:26 peter Exp $
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SRCS+= boot.c commands.c console.c devopen.c interp.c interp_backslash.c
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SRCS+= interp_parse.c load_aout.c load_elf.c ls.c misc.c module.c panic.c
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SRCS+= bcache.c boot.c commands.c console.c devopen.c interp.c
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SRCS+= interp_backslash.c interp_parse.c load_aout.c load_elf.c ls.c misc.c
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SRCS+= module.c panic.c
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# Machine-independant ISA PnP
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.if HAVE_ISABUS
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227
sys/boot/common/bcache.c
Normal file
227
sys/boot/common/bcache.c
Normal file
@ -0,0 +1,227 @@
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/*
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* mjs copyright
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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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};
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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 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_stamp = 0;
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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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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;
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time(&now);
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/* find the oldest block */
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for (cand = 0, 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_stamp < now)
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cand = i;
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}
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DEBUG("insert blk %d -> %d @ %d", blkno, cand, now);
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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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}
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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(" %02x: %08x %04x", i, bcache_ctl[i].bc_blkno, bcache_ctl[i].bc_stamp & 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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@ -23,7 +23,7 @@
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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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* $Id: bootstrap.h,v 1.14 1998/10/21 20:07:04 msmith Exp $
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* $Id: bootstrap.h,v 1.15 1998/10/22 20:20:50 msmith Exp $
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*/
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#include <sys/types.h>
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@ -71,6 +71,15 @@ extern void hexdump(caddr_t region, size_t len);
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extern size_t strlenout(vm_offset_t str);
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extern char *strdupout(vm_offset_t str);
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/*
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* Disk block cache
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*/
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struct bcache_devdata
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{
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int (*dv_strategy)(void *devdata, int rw, daddr_t blk, size_t size, void *buf, size_t *rsize);
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void *dv_devdata;
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};
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/*
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* Modular console support.
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*/
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@ -23,7 +23,7 @@
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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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* $Id: biosdisk.c,v 1.15 1998/10/30 07:15:52 luoqi Exp $
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* $Id: biosdisk.c,v 1.16 1998/10/31 02:53:11 msmith Exp $
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*/
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/*
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@ -103,6 +103,7 @@ static int bd_int13probe(struct bdinfo *bd);
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static int bd_init(void);
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static int bd_strategy(void *devdata, int flag, daddr_t dblk, size_t size, void *buf, size_t *rsize);
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static int bd_realstrategy(void *devdata, int flag, daddr_t dblk, size_t size, void *buf, size_t *rsize);
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static int bd_open(struct open_file *f, ...);
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static int bd_close(struct open_file *f);
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static void bd_print(int verbose);
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@ -494,6 +495,16 @@ bd_closedisk(struct open_disk *od)
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static int
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bd_strategy(void *devdata, int rw, daddr_t dblk, size_t size, void *buf, size_t *rsize)
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{
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struct bcache_devdata bcd;
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bcd.dv_strategy = bd_realstrategy;
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bcd.dv_devdata = devdata;
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return(bcache_strategy(&bcd, rw, dblk, size, buf, rsize));
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}
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static int
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bd_realstrategy(void *devdata, int rw, daddr_t dblk, size_t size, void *buf, size_t *rsize)
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{
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struct open_disk *od = (struct open_disk *)(((struct i386_devdesc *)devdata)->d_kind.biosdisk.data);
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int blks;
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@ -23,7 +23,7 @@
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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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||||
* $Id: main.c,v 1.12 1998/10/21 20:10:33 msmith Exp $
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* $Id: main.c,v 1.13 1998/10/22 20:23:58 msmith Exp $
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*/
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/*
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@ -97,6 +97,11 @@ main(void)
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setenv("console", "comconsole", 1);
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cons_probe();
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||||
/*
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||||
* Initialise the block cache
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||||
*/
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||||
bcache_init(32, 512); /* 16k cache XXX tune this */
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||||
/*
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* March through the device switch probing for things.
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*/
|
||||
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||||
Loading…
Reference in New Issue
Block a user