Messages in this thread | | | Date | Tue, 05 Aug 2008 01:09:21 +0200 | From | Rene Herman <> | Subject | Re: No, really, stop trying to delete slab until you've finished making slub perform as well |
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On 04-08-08 23:41, Christoph Lameter wrote:
>>> General interested question -- I recently "accidentally" read some of >>> slub and I believe that it doesn't feature the cache colouring support >>> that slab did? Is that true, and if so, wasn't it needed/useful? >> I don't know why Christoph decided not to implement it. Christoph? > > IMHO cache coloring issues seem to be mostly taken care of by newer more > associative cpu caching designs.
I see. Just gathered a bit of data on this (from sandpile.org):
32-byte lines:
P54 : L1 I 8K, 2-Way D 8K, 2-Way L2 External
P55 : L1 I 16K, 4-Way D 16K, 4-Way L2 External
P2 : L1 I 16K 4-Way D 16K 4-Way L2 128K to 2MB 4-Way
P3 : L1 I 16K 4-Way D 16K 4-Way L2 128K to 2MB 4-Way or 256K to 2MB 8-Way
64-byte lines:
P4 : L1 I 12K uOP Trace (8-Way, 6 uOP line) D 8K 4-Way or 16K 8-Way L2 128K 2-Way or 128K, 256K 4-Way or 512K, 1M, 2M 8-Way L3 512K 4-Way or 1M to 8M 8-Way or 2M to 16M 16-Way
Core: L1 I 32K 8-Way D 32K 8-Way L2 512K 2-Way or 1M 4-Way or 2M 8-Way or 3M 12-Way or 4M 16-Way
K7 : L1 I 64K 2-Way D 64K 2-Way L2 512, 1M, 2M 2-Way or 4M, 8M 1-Way or 64K, 256K, 512K 16-Way
K8 : L1 I 64K 2-Way D 64K 2-Way L2 128K to 1M 16-Way
The L1 on K7 and K8 especially seems still a bit of worry here.
> Note that the SLAB design origin is Solaris (See the paper by Jeff Bonwick in > 1994 that is quoted in mm/slab.c). Logic for cache coloring is mostly avoided > today due to the complexity it would introduce. See also > http://en.wikipedia.org/wiki/CPU_cache. > > What one could add to support cache coloring in SLUB is a prearrangement of > the order of object allocation order by constructing the initial freelist for > a page in a certain way. See mm/slub.c::new_slab()
<remains silent>
To me, colouring always seemed like a fairly promising thing but I won't pretend to have any sort of data.
Rene.
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