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Add fix-stack-lzjb topic branch 

Reduce kernel stack usage by lzjb_compress() by moving uint16 array
off the stack and on to the heap.  The exact performance implications
of this I have not measured but we absolutely need to keep stack
usage to a minimum.  If/when this becomes and issue we optimize.
This commit is contained in:
Brian Behlendorf 2010-06-14 16:45:01 -07:00
parent 428870ff73
commit b8cc785fb6
3 changed files with 18 additions and 3 deletions
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.topdeps Normal file
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From: Brian Behlendorf <behlendorf1@llnl.gov>
Subject: [PATCH] fix stack lzjb
Reduce kernel stack usage by lzjb_compress() by moving uint16 array
off the stack and on to the heap. The exact performance implications
of this I have not measured but we absolutely need to keep stack
usage to a minimum. If/when this becomes and issue we optimize.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>

11
module/zfs/lzjb.c
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@ -37,7 +37,7 @@
* compress to d_len or less.
*/
#include <sys/types.h>
#include <sys/zfs_context.h>
#define MATCH_BITS 6
#define MATCH_MIN 3
@ -55,12 +55,15 @@ lzjb_compress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n)
int copymask = 1 << (NBBY - 1);
int mlen, offset, hash;
uint16_t *hp;
uint16_t lempel[LEMPEL_SIZE] = { 0 };
uint16_t *lempel;
lempel = kmem_zalloc(LEMPEL_SIZE * sizeof (uint16_t), KM_SLEEP);
while (src < (uchar_t *)s_start + s_len) {
if ((copymask <<= 1) == (1 << NBBY)) {
if (dst >= (uchar_t *)d_start + d_len - 1 - 2 * NBBY)
if (dst >= (uchar_t *)d_start + d_len - 1 - 2 * NBBY) {
kmem_free(lempel, LEMPEL_SIZE*sizeof(uint16_t));
return (s_len);
}
copymask = 1;
copymap = dst;
*dst++ = 0;
@ -90,6 +93,8 @@ lzjb_compress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n)
*dst++ = *src++;
}
}
kmem_free(lempel, LEMPEL_SIZE * sizeof (uint16_t));
return (dst - (uchar_t *)d_start);
}