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Implement simple write combining for newfs - this is particularly useful

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for large scsi disks with WCE = 0.  This yields around a 7 times speedup
on elapsed newfs time on test disks here.  64k clusters seems to be the
sweet spot for scsi disks using our present drivers.
This commit is contained in:
Peter Wemm 2000-10-17 00:41:36 +00:00
parent 242fae60f0
commit 3927beeda1
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=67239
1 changed files with 37 additions and 0 deletions
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37
sbin/newfs/mkfs.c
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@ -1324,6 +1324,11 @@ rdfs(bno, size, bf)
}
}
#define WCSIZE (128 * 1024)
daddr_t wc_sect; /* units of sectorsize */
int wc_end; /* bytes */
static char wc[WCSIZE]; /* bytes */
/*
* write a block to the file system
*/
@ -1334,6 +1339,7 @@ wtfs(bno, size, bf)
char *bf;
{
int n;
int done;
if (mfs) {
memmove(membase + bno * sectorsize, bf, size);
@ -1341,6 +1347,37 @@ wtfs(bno, size, bf)
}
if (Nflag)
return;
done = 0;
if (wc_end == 0 && size <= WCSIZE) {
wc_sect = bno;
bcopy(bf, wc, size);
wc_end = size;
if (wc_end < WCSIZE)
return;
done = 1;
}
if (wc_sect * sectorsize + wc_end == bno * sectorsize &&
wc_end + size <= WCSIZE) {
bcopy(bf, wc + wc_end, size);
wc_end += size;
if (wc_end < WCSIZE)
return;
done = 1;
}
if (wc_end) {
if (lseek(fso, (off_t)wc_sect * sectorsize, SEEK_SET) < 0) {
printf("seek error: %ld\n", (long)wc_sect);
err(35, "wtfs - writecombine");
}
n = write(fso, wc, wc_end);
if (n != wc_end) {
printf("write error: %ld\n", (long)wc_sect);
err(36, "wtfs - writecombine");
}
wc_end = 0;
}
if (done)
return;
if (lseek(fso, (off_t)bno * sectorsize, SEEK_SET) < 0) {
printf("seek error: %ld\n", (long)bno);
err(35, "wtfs");