Messages in this thread | | | Date | Wed, 22 Feb 2006 11:40:08 +1100 | From | Nick Piggin <> | Subject | Re: [patch] Cache align futex hash buckets |
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Christoph Lameter wrote: > On Tue, 21 Feb 2006, Nick Piggin wrote: > > >>Ravikiran G Thirumalai wrote: >> >>>Following change places each element of the futex_queues hashtable on a >>>different cacheline. Spinlocks of adjacent hash buckets lie on the same >>>cacheline otherwise. >>> >> >>It does not make sense to add swaths of unused memory into a hashtable for >>this purpose, does it? > > > It does if you essentially have a 4k cacheline (because you are doing NUMA > in software with multiple PCs....) and transferring control of that > cacheline is comparatively expensive. >
Instead of 1MB hash with 256 entries in it covering 256 cachelines, you have a 1MB hash with 65536(ish) entries covering 256 cachelines.
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