Messages in this thread | | | Date | Tue, 21 Feb 2006 18:08:45 -0800 | From | Andrew Morton <> | Subject | Re: [patch] Cache align futex hash buckets |
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Nick Piggin <nickpiggin@yahoo.com.au> wrote: > > 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. >
Good (if accidental point). Kiran, if you're going to gobble a megabyte, you might as well use all of it and make the hashtable larger, rather than just leaving 99% of that memory unused... - 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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