On Thu, Jan 22, 2015 at 07:31:53PM -0800, Jason Low wrote: > When 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 the 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%.
I'll have to look; I worry about consistency between the values. But why would any self respecting piece of software use this crap stuff? Its a guaranteed scalability fail. -- 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/