Messages in this thread | ![/](/images/icornerl.gif) | | Date | Sun, 23 Mar 2003 16:51:37 -0500 | From | Brian Gerst <> | Subject | Re: [PATCH] slab.c cleanup |
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Manfred Spraul wrote: > Brian Gerst wrote: > >> >> Perhaps, but it currently is already allocating 128 bytes for smaller >> caches, because the cache is created with SLAB_HWCACHE_ALIGN. So we >> ended up with redundantly sized caches. >> > > linux/mm/slab.c: > >> if (flags & SLAB_HWCACHE_ALIGN) { >> /* Need to adjust size so that objs are cache aligned. */ >> /* Small obj size, can get at least two per cache line. */ >> while (size < align/2) >> align /= 2; >> size = (size+align-1)&(~(align-1)); >> } >> >> > HWALIGN is just a hint, the implementation ignores it if it results in > unreasonable wasting of memory.
I think I see what was causing be to believe it was always rounding up to the cache size. The while test should be while (size <= align/2). On my machine (athlon, 64 byte cache), the size-32 cache was rounded up to 64 bytes because of this.
size-128 1416 1470 128 49 49 1 : 248 124 size-64 351 413 64 7 7 1 : 248 124 size-32 649 649 64 11 11 1 : 248 124 ^^^^
-- Brian Gerst
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