On Tue, 2015-04-14 at 16:09 -0700, Jason Low wrote: > While running a database workload, we found a scalability issue with itimers. > > Much of the problem was caused by the thread_group_cputimer spinlock. > Each time we account for group system/user time, we need to obtain a > thread_group_cputimer's spinlock to update the timers. On larger systems > (such as a 16 socket machine), this caused more than 30% of total time > spent trying to obtain this kernel lock to update these group timer stats. > > This patch converts the timers to 64 bit atomic variables and use > atomic add to update them without a lock. With this patch, the percent > of total time spent updating thread group cputimer timers was reduced > from 30% down to less than 1%.
What does 30% less time spent dealing with the thread_group_cputimer's spinlock buy us? iow, does this help DB benchmark throughput or such? Thanks, Davidlohr -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
