Messages in this thread Patch in this message | | | Date | Sun, 26 Jun 2011 21:39:18 +0200 | From | Marcin Slusarz <> | Subject | [PATCH] slub: reduce overhead of slub_debug |
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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 --- mm/slub.c | 36 ++++++++++++++++++++++++++++++++++-- 1 files changed, 34 insertions(+), 2 deletions(-)
diff --git a/mm/slub.c b/mm/slub.c index 35f351f..a40ef2d 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -557,10 +557,10 @@ 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--; @@ -568,6 +568,38 @@ 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) { -- 1.7.5.3
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