On 01/05/2011 10:40 AM, KOSAKI Motohiro wrote:
> 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. I'm sure you haven't try your scheme. but I did. It's slow.
Won't anything with a heavily contented global/giant lock be slow? What's the average lock hold time per thread? 10%? 50%? 90%? -- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
