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slub: reduce overhead of slub_debug 

slub checks for poison one byte by one, which is highly inefficient
and shows up frequently as a highest cpu-eater in perf top.

Joining reads gives nice speedup:

(Compiling some project with different options)
                                 make -j12    make clean
slub_debug disabled:             1m 27s       1.2 s
slub_debug enabled:              1m 46s       7.6 s
slub_debug enabled + this patch: 1m 33s       3.2 s

check_bytes still shows up high, but not always at the top.

Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Matt Mackall <mpm@selenic.com>
Cc: linux-mm@kvack.org
Signed-off-by: Pekka Enberg <penberg@kernel.org>
This commit is contained in:
Marcin Slusarz 2011-06-26 21:39:18 +02:00 committed by Pekka Enberg
parent d18a90dd85
commit c4089f98e9
1 changed files with 34 additions and 2 deletions
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36
mm/slub.c
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@ -589,10 +589,10 @@ static void init_object(struct kmem_cache *s, void *object, u8 val)
memset(p + s->objsize, val, s->inuse - s->objsize);
}
static u8 *check_bytes(u8 *start, unsigned int value, unsigned int bytes)
static u8 *check_bytes8(u8 *start, u8 value, unsigned int bytes)
{
while (bytes) {
if (*start != (u8)value)
if (*start != value)
return start;
start++;
bytes--;
@ -600,6 +600,38 @@ static u8 *check_bytes(u8 *start, unsigned int value, unsigned int bytes)
return NULL;
}
static u8 *check_bytes(u8 *start, u8 value, unsigned int bytes)
{
u64 value64;
unsigned int words, prefix;
if (bytes <= 16)
return check_bytes8(start, value, bytes);
value64 = value | value << 8 | value << 16 | value << 24;
value64 = value64 | value64 << 32;
prefix = 8 - ((unsigned long)start) % 8;
if (prefix) {
u8 *r = check_bytes8(start, value, prefix);
if (r)
return r;
start += prefix;
bytes -= prefix;
}
words = bytes / 8;
while (words) {
if (*(u64 *)start != value64)
return check_bytes8(start, value, 8);
start += 8;
words--;
}
return check_bytes8(start, value, bytes % 8);
}
static void restore_bytes(struct kmem_cache *s, char *message, u8 data,
void *from, void *to)
{