On Tue, Feb 25, 2014 at 10:13:11AM -0800, Junjie Qian wrote: > Dear all, > > I am working on one project, which tries to profile the lock stats for one > application, such as total waiting time for locks or how many locks happens > during the execution.
perf lock wouldn't help with that, IIUC. perf lock is for locks inside the kernel. There are ways (not sure if the patch is in) to track for lock contension using perf, but not sure (I think not easy at least) if the lock is not contended. As, if using glibc, lot of locks are implemented using futex and then solved entirely in userspace lot of times (at least without contention). Also, about stats such as the total waiting time, take into account that if you have more threads than cores, there WILL be waiting time you can't reduce. For some experiments I did (with #threads >> #cores) trying to measure waiting time was pointeless, as that didn't help us in any way. And in some scenarios (cpu hungry tasks, for example), it's not important to have threads waiting if all your cores are active "most of the time". So, for me (for my workloads), the waiting time was pointless and it was WAY more useful trying to see "wasted" time. As I was trying to optimize a library, I did some instrumentation on it to get the CPU time used by the library and compare it against #cores * elapsed_time. Hope it helps, Rodrigo -- To unsubscribe from this list: send the line "unsubscribe linux-perf-users" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
