Messages in this thread Patch in this message | | | Date | Sat, 3 Nov 2007 17:10:54 +0000 (GMT) | From | Hugh Dickins <> | Subject | [PATCH 1/2] slub: fix leakage |
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Slub has been quite leaky under load. Taking mm_struct as an example, in a loop of swapping kernel builds, after the first iteration slabinfo shows: Name Objects Objsize Space Slabs/Part/Cpu O/S O %Fr %Ef Flg mm_struct 55 840 73.7K 18/7/4 4 0 38 62 A but Objects and Partials steadily creep up - after the 340th iteration: mm_struct 110 840 188.4K 46/36/4 4 0 78 49 A
The culprit turns out to be __slab_alloc(), where it copes with the race that another task has assigned the cpu slab while we were allocating one. Don't rush off to load_freelist there: that assumes c->freelist is empty, and will lose all of its free slots when c->page->freelist is not empty. Instead just do a local allocation from c->freelist when it has one.
Which fixes the leakage: Objects and Partials then remain stable.
Signed-off-by: Hugh Dickins <hugh@veritas.com> --- I recommend this for 2.6.24-rc2 and 2.6.23-stable.
mm/slub.c | 5 +++++ 1 file changed, 5 insertions(+)
--- 2.6.24-rc1/mm/slub.c 2007-10-24 07:16:04.000000000 +0100 +++ linux/mm/slub.c 2007-11-03 13:22:31.000000000 +0000 @@ -1525,6 +1525,11 @@ new_slab: * want the current one since its cache hot */ discard_slab(s, new); + if (c->freelist) { + object = c->freelist; + c->freelist = object[c->offset]; + return object; + } slab_lock(c->page); goto load_freelist; } - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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