Add a 3rd entry in the cache, which keeps the end position

from just before extending a file.  This has the desired effect
of keeping the write speed constant.  And yes, that helps a lot
copying large files always at full speed now, and I have seen
improvements using benchmarks/bonnie.

Stolen from:	NetBSD
Reviewed by:	bde
This commit is contained in:
Tom Rhodes 2007-01-16 23:43:14 +00:00
parent e8ac01c56a
commit 752945d6c0
2 changed files with 19 additions and 3 deletions
sys/fs/msdosfs

@ -116,10 +116,12 @@ struct fatcache {
* cache is probably pretty worthless if a file is opened by multiple
* processes.
*/
#define FC_SIZE 2 /* number of entries in the cache */
#define FC_SIZE 3 /* number of entries in the cache */
#define FC_LASTMAP 0 /* entry the last call to pcbmap() resolved
* to */
#define FC_LASTFC 1 /* entry for the last cluster in the file */
#define FC_NEXTTOLASTFC 2 /* entry for a close to the last cluster in
* the file */
#define FCE_EMPTY 0xffffffff /* doesn't represent an actual cluster # */
@ -130,6 +132,13 @@ struct fatcache {
(dep)->de_fc[(slot)].fc_frcn = (frcn); \
(dep)->de_fc[(slot)].fc_fsrcn = (fsrcn);
#define fc_last_to_nexttolast(dep) do { \
(dep)->de_fc[FC_NEXTTOLASTFC].fc_frcn = \
(dep)->de_fc[FC_LASTFC].fc_frcn; \
(dep)->de_fc[FC_NEXTTOLASTFC].fc_fsrcn = \
(dep)->de_fc[FC_LASTFC].fc_fsrcn; \
} while (0)
/*
* This is the in memory variant of a dos directory entry. It is usually
* contained within a vnode.

@ -79,6 +79,8 @@ static int fc_bmapcalls; /* # of times pcbmap was called */
static int fc_lmdistance[LMMAX];/* counters for how far off the last
* cluster mapped entry was. */
static int fc_largedistance; /* off by more than LMMAX */
static int fc_wherefrom, fc_whereto, fc_lastclust;
static int pm_fatblocksize;
static int chainalloc(struct msdosfsmount *pmp, u_long start,
u_long count, u_long fillwith, u_long *retcluster,
@ -119,6 +121,7 @@ fatblock(pmp, ofs, bnp, sizep, bop)
*sizep = size;
if (bop)
*bop = ofs % pmp->pm_fatblocksize;
pm_fatblocksize = pmp->pm_fatblocksize;
}
/*
@ -210,9 +213,12 @@ pcbmap(dep, findcn, bnp, cnp, sp)
*/
i = 0;
fc_lookup(dep, findcn, &i, &cn);
if ((bn = findcn - i) >= LMMAX)
if ((bn = findcn - i) >= LMMAX) {
fc_largedistance++;
else
fc_wherefrom = i;
fc_whereto = findcn;
fc_lastclust = dep->de_fc[FC_LASTFC].fc_frcn;
} else
fc_lmdistance[bn]++;
/*
@ -1025,6 +1031,7 @@ extendfile(dep, count, bpp, ncp, flags)
return (error);
}
fc_last_to_nexttolast(dep);
while (count > 0) {
/*
* Allocate a new cluster chain and cat onto the end of the