Hi Everyone, I have a profiling tool question that could go beyond perf.
In an application, there are threads blocking on epoll_wait(). The file descriptors are sockets connecting to other servers in a data center with less than 1ms network latency. On normal systems, the delay to wake up epoll_wait is much less than 1ms. It is noticed on a system that sometimes it takes an unbelievable 30ms delay to wake up the thread blocking in epoll_wait(). To be exact, the delay of reference here is between tcp_rcv_established() and epoll_wait.return. I wonder whether there is a way to dump out the stack trace of threads, or some other kernel entities, that wake up that thread. The idea is to figure out why there is a huge delay by looking at how the delayed is ended, and by whom/what. epoll wakeup internels in the kernel space can be referred to at http://www.slideshare.net/llj098/epoll-from-the-kernel-side. As a reference, there is a dtrace script that does this on Solaris. https://github.com/brendangregg/dtrace-cloud-tools/blob/master/system/cv_wakeup_slow.d Would perf/systemTap or other Linux tools be helpful? Thanks, Jun -- 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
