sched_wakeup_new and sched_kthread_stop events cause great overload
in [Kernel]
|
Prev: [PATCH 1/3] resource: shared I/O region support
Next: trace-cmd: Add BUILDING and INSTALL instructions to README
From: Steven Rostedt on 25 Mar 2010 09:40 On Thu, 2010-03-25 at 17:36 +0800, Xiao Guangrong wrote: > We have done sysbench test for ftrace's performance and it looks sched_wakeup_new > and sched_kthread_stop events can cause great overload. > > When we only enable sched_wakeup_new and sched_kthread_stop events, sysbench.threads > shows the overload is 10%, sysbench.mutex shows the overload is 7.5%. > > The more weird thing is that we found the sched_kthread_stop event is never called > in this test, the test steps as follow: > > echo > debugfs/tracing/set_event > echo 1 > debugfs/tracing/events/sched/sched_wakeup_new/enable > echo 1 > debugfs/tracing/events/sched/sched_kthread_stop/enable > > com_opt="--num-threads=5000 --max-requests=50000" > echo > debugfs/tracing/trace > sysbench $com_opt --test=threads --thread-yields=1000 --thread-locks=10000 run >& log > [or sysbench $com_opt --test=mutex --mutex-num=100 --mutex-locks=50000 --mutex-loops=10000 run for mutex] > echo > debugfs/tracing/set_event > > For sysbench.threads: > cat debugfs/tracing/trace | grep "sched_wakeup_new" | wc -l > 5001 > cat debugfs/tracing/trace | grep "sched_kthread_stop" | wc -l > 0 Strange? So if you did: cat debugfs/tracing/trace | wc -l you should get 5005? > > For sysbench.mutex: > cat debugfs/tracing/trace | grep "sched_wakeup_new" | wc -l > 5001 > cat debugfs/tracing/trace | grep "sched_kthread_stop" | wc -l > 0 > > And, if only enable sched_kthread_stop event, the sysbench.threads's > overload is 5.90%, the sysbench.mutex's overload is 3.36%. Could be something that messes with the cache lines? > > It hardly explain why sched_kthread_stop is never called but cause great overload. Would be worth running perf against this test, to see where the issues are occurring. -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |