On Thursday, March 9, 2017 4:38 PM Steven Rostedt [mailto:rostedt@xxxxxxxxxxx] wrote: > On Thu, 9 Mar 2017 15:30:42 +0000 > "Dorau, Lukasz" <lukasz.dorau@xxxxxxxxx> wrote: > > > On Thursday, March 9, 2017 4:21 PM Steven Rostedt wrote: > > > On Thu, 9 Mar 2017 15:01:38 +0000 (UTC) > > > Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx> wrote: > > > > > > > > > > Another more likely scenario is if a multithreaded process > > > > has many threads blocked (e.g. on a futex), and one of the threads > > > > exits cleanly or forks. I suspect the kernel will just tear down the > > > > other threads without hitting syscall exit. > > > > > > Maybe, if this happens multiple times, it could cause those kinds of > > > numbers. A fork was done zero times according to the numbers. Maybe > > > exit should be measured too. > > > > > > > I have run the test again with exit: > > > > Results (60 sec): > > futex: p 2968 r 401 (86% did not return (2567)) > > poll: p 13251 r 3957 (70% did not return (9294)) > > epoll_wait: p 1485 r 556 (62% did not return (929)) > > select: p 8063 r 8066 (OK) > > fork: p 0 r 0 (OK) > > vfork: p 4 r 4 (OK) > > clone: p 6962 r 6962 (OK) > > exit: p 3 r 0 (100% did not return (3)) > > I expected exit not to have a return, that's the property of exit. But > it shows that the above poll and friends is not because of exit and > fork. > > Can you change your script to use syscall tracepoints instead of > retprobes? > Here you are: https://gist.github.com/ldorau/36d87640ff0659a483342d490b66f034 KProbes results (60 sec): futex: p 14671 r 1808 (87% did not return (12863)) poll: p 31833 r 2099 (93% did not return (29734)) epoll_wait: p 20852 r 4761 (77% did not return (16091)) select: p 12331 r 12327 (0% did not return (4)) mmap: p 2090 r 2090 (OK) open: p 4155 r 4155 (OK) close: p 4720 r 4720 (OK) write: p 11328 r 11328 (OK) read: p 22233 r 22233 (OK) exit: p 14 r 0 (100% did not return (14)) fork: p 0 r 0 (OK) vfork: p 0 r 0 (OK) clone: p 48 r 48 (OK) execve: p 17 r 17 (OK) Tracepoints results (60 sec): futex: p 14639 r 14632 (0% did not return (7)) poll: p 31833 r 31834 (OK) epoll_wait: p 20852 r 20852 (OK) select: p 12330 r 12328 (0% did not return (2)) mmap: p 2090 r 2090 (OK) open: p 4155 r 4171 (OK) close: p 4720 r 4720 (OK) write: p 11327 r 11328 (OK) read: p 22233 r 22233 (OK) exit: p 14 r 0 (100% did not return (14)) Lukasz -- To unsubscribe from this list: send the line "unsubscribe linux-trace-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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