Messages in this thread | | | Date | Wed, 07 Apr 2010 19:52:56 +0300 | From | Pekka Enberg <> | Subject | Re: hackbench regression due to commit 9dfc6e68bfe6e |
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Pekka Enberg wrote: > Christoph Lameter wrote: >> I wonder if this is not related to the kmem_cache_cpu structure >> straggling >> cache line boundaries under some conditions. On 2.6.33 the kmem_cache_cpu >> structure was larger and therefore tight packing resulted in different >> alignment. >> >> Could you see how the following patch affects the results. It attempts to >> increase the size of kmem_cache_cpu to a power of 2 bytes. There is also >> the potential that other per cpu fetches to neighboring objects affect >> the >> situation. We could cacheline align the whole thing. >> >> --- >> include/linux/slub_def.h | 5 +++++ >> 1 file changed, 5 insertions(+) >> >> Index: linux-2.6/include/linux/slub_def.h >> =================================================================== >> --- linux-2.6.orig/include/linux/slub_def.h 2010-04-07 >> 11:33:50.000000000 -0500 >> +++ linux-2.6/include/linux/slub_def.h 2010-04-07 >> 11:35:18.000000000 -0500 >> @@ -38,6 +38,11 @@ struct kmem_cache_cpu { >> void **freelist; /* Pointer to first free per cpu object */ >> struct page *page; /* The slab from which we are allocating */ >> int node; /* The node of the page (or -1 for debug) */ >> +#ifndef CONFIG_64BIT >> + int dummy1; >> +#endif >> + unsigned long dummy2; >> + >> #ifdef CONFIG_SLUB_STATS >> unsigned stat[NR_SLUB_STAT_ITEMS]; >> #endif > > Would __cacheline_aligned_in_smp do the trick here?
Oh, sorry, I think it's actually '____cacheline_aligned_in_smp' (with four underscores) for per-cpu data. Confusing...
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