Messages in this thread | | | Date | Wed, 05 Jan 2011 10:35:44 +0200 | From | Avi Kivity <> | Subject | Re: [RFC -v3 PATCH 2/3] sched: add yield_to function |
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On 01/05/2011 04:39 AM, KOSAKI Motohiro wrote: > > On 01/04/2011 08:14 AM, KOSAKI Motohiro wrote: > > > Also, If pthread_cond_signal() call sys_yield_to imlicitly, we can > > > avoid almost Nehalem (and other P2P cache arch) lock unfairness > > > problem. (probaby creating pthread_condattr_setautoyield_np or similar > > > knob is good one) > > > > Often, the thread calling pthread_cond_signal() wants to continue > > executing, not yield. > > Then, it doesn't work. > > After calling pthread_cond_signal(), T1 which cond_signal caller and T2 > which waked start to GIL grab race. But usually T1 is always win because > lock variable is in T1's cpu cache. Why kernel and userland have so much > different result? One of a reason is glibc doesn't have any ticket lock scheme. > > If you are interesting GIL mess and issue, please feel free to ask more.
I suggest looking into an explicit round-robin scheme, where each thread adds itself to a queue and an unlock wakes up the first waiter.
-- error compiling committee.c: too many arguments to function
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