Messages in this thread | | | Subject | Re: [RFC PATCH 0/5] futex: introduce an optimistic spinning futex | From | Davidlohr Bueso <> | Date | Mon, 21 Jul 2014 17:32:55 -0700 |
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On Mon, 2014-07-21 at 14:31 -0700, Andy Lutomirski wrote: > On Mon, Jul 21, 2014 at 2:27 PM, Peter Zijlstra <peterz@infradead.org> wrote: > > All this is predicated on the fact that syscalls are 'expensive'. > > Weren't syscalls only 100s of cycles? All this bitmap mucking is far > > more expensive due to cacheline misses, which due to the size of the > > things is almost guaranteed. > > 120 - 300 cycles for me, unless tracing happens, and I'm working on > reducing the incidence of tracing.
fwiw here's what lmbench's lat_ctx says on my system . For 'accuracy', I kept the runs short.
http://www.stgolabs.net/lat_ctx.png
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