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Gather writes to larger chunks (MAXPHYS) instead of issuing them in

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sectors.

On my SanDisk Cruzer Blade 16GB USB stick this made formatting much faster:

x before
+ after
+--------------------------------------------------------------------------+
|+                                                                         |
|+                                                                      x  |
|+                                                                      x x|
|A                                                                      MA||
+--------------------------------------------------------------------------+
    N           Min           Max        Median           Avg        Stddev
x   3         15.89         16.38            16         16.09     0.2570992
+   3          0.32          0.37          0.35    0.34666667   0.025166115
Difference at 95.0% confidence
	-15.7433 +/- 0.414029
	-97.8455% +/- 0.25668%
	(Student's t, pooled s = 0.182665)

Reviewed by:	emaste
MFC after:	2 weeks
Differential Revision:	https://reviews.freebsd.org/D24508
This commit is contained in:
delphij 2020-07-04 18:37:04 +00:00
parent c70dfe3ca2
commit 12cee841c6
1 changed files with 58 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

76
sbin/newfs_msdos/mkfs_msdos.c
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@ -64,6 +64,7 @@ static const char rcsid[] =
#define DOSMAGIC 0xaa55 /* DOS magic number */
#define MINBPS 512 /* minimum bytes per sector */
#define MAXBPS 4096 /* maximum bytes per sector */
#define MAXSPC 128 /* maximum sectors per cluster */
#define MAXNFT 16 /* maximum number of FATs */
#define DEFBLK 4096 /* default block size */
@ -77,6 +78,25 @@ static const char rcsid[] =
#define MAXCLS16 0xfff4U /* maximum FAT16 clusters */
#define MAXCLS32 0xffffff4U /* maximum FAT32 clusters */
#ifndef CTASSERT
#define CTASSERT(x) _CTASSERT(x, __LINE__)
#define _CTASSERT(x, y) __CTASSERT(x, y)
#define __CTASSERT(x, y) typedef char __assert_ ## y [(x) ? 1 : -1]
#endif
/*
* For better performance, we want to write larger chunks instead of
* individual sectors (the size can only be 512, 1024, 2048 or 4096
* bytes). Assert that MAXPHYS can always hold an integer number of
* sectors by asserting that both are power of two numbers and the
* MAXPHYS is greater than MAXBPS.
*/
CTASSERT(powerof2(MAXPHYS));
CTASSERT(powerof2(MAXBPS));
CTASSERT(MAXPHYS > MAXBPS);
const static ssize_t chunksize = MAXPHYS;
#define mincls(fat) ((fat) == 12 ? MINCLS12 : \
(fat) == 16 ? MINCLS16 : \
MINCLS32)
@ -243,6 +263,7 @@ mkfs_msdos(const char *fname, const char *dtype, const struct msdos_options *op)
struct bsx *bsx;
struct de *de;
u_int8_t *img;
u_int8_t *physbuf, *physbuf_end;
const char *bname;
ssize_t n;
time_t now;
@ -252,7 +273,7 @@ mkfs_msdos(const char *fname, const char *dtype, const struct msdos_options *op)
int fd, fd1, rv;
struct msdos_options o = *op;
img = NULL;
physbuf = NULL;
rv = -1;
fd = fd1 = -1;
@ -343,13 +364,11 @@ mkfs_msdos(const char *fname, const char *dtype, const struct msdos_options *op)
bpb.bpbSecPerClust = 64; /* otherwise 32k */
}
}
if (!powerof2(bpb.bpbBytesPerSec)) {
warnx("bytes/sector (%u) is not a power of 2", bpb.bpbBytesPerSec);
goto done;
}
if (bpb.bpbBytesPerSec < MINBPS) {
warnx("bytes/sector (%u) is too small; minimum is %u",
bpb.bpbBytesPerSec, MINBPS);
if (bpb.bpbBytesPerSec < MINBPS ||
bpb.bpbBytesPerSec > MAXBPS ||
!powerof2(bpb.bpbBytesPerSec)) {
warnx("Invalid bytes/sector (%u): must be 512, 1024, 2048 or 4096",
bpb.bpbBytesPerSec);
goto done;
}
@ -621,11 +640,14 @@ mkfs_msdos(const char *fname, const char *dtype, const struct msdos_options *op)
tm = localtime(&now);
}
if (!(img = malloc(bpb.bpbBytesPerSec))) {
physbuf = malloc(chunksize);
if (physbuf == NULL) {
warn(NULL);
goto done;
}
physbuf_end = physbuf + chunksize;
img = physbuf;
dir = bpb.bpbResSectors + (bpb.bpbFATsecs ? bpb.bpbFATsecs :
bpb.bpbBigFATsecs) * bpb.bpbFATs;
memset(&si_sa, 0, sizeof(si_sa));
@ -750,19 +772,37 @@ mkfs_msdos(const char *fname, const char *dtype, const struct msdos_options *op)
(u_int)tm->tm_mday;
mk2(de->deMDate, x);
}
if ((n = write(fd, img, bpb.bpbBytesPerSec)) == -1) {
warn("%s", fname);
goto done;
}
if ((unsigned)n != bpb.bpbBytesPerSec) {
warnx("%s: can't write sector %u", fname, lsn);
goto done;
/*
* Issue a write of chunksize once we have collected
* enough sectors.
*/
img += bpb.bpbBytesPerSec;
if (img >= physbuf_end) {
n = write(fd, physbuf, chunksize);
if (n != chunksize) {
warnx("%s: can't write sector %u", fname, lsn);
goto done;
}
img = physbuf;
}
}
/*
* Write remaining sectors, if the last write didn't end
* up filling a whole chunk.
*/
if (img != physbuf) {
ssize_t tailsize = img - physbuf;
n = write(fd, physbuf, tailsize);
if (n != tailsize) {
warnx("%s: can't write sector %u", fname, lsn);
goto done;
}
}
}
rv = 0;
done:
free(img);
free(physbuf);
if (fd != -1)
close(fd);
if (fd1 != -1)