Messages in this thread | | | Date | Tue, 13 Jan 2015 12:25:16 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH RESEND v4] sched/fair: Add advisory flag for borrowing a timeslice |
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On Tue, Dec 23, 2014 at 01:46:58PM -0500, Rik van Riel wrote: > An uncontended futex is taken without ever going into kernel > space. Adaptive spinning allows short duration futexes to be > taken without going into kernel space.
The going into kernel is a red herring afaict, a no-op syscall costs ~180 cycles or something like that. So sure you can do a wee spin (~90 cycles to try and amortize that), but I really doubt that this is the problem.
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