Nick Piggin <[email protected]> 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...
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