2016-04-18 4:04 GMT+02:00 Rowan Worth <rowanw at dugeo.com>: > On 18 April 2016 at 06:55, Cecil Westerhof <cldwesterhof at gmail.com> wrote: > > > ?I put a strace on it. This was what I got: > > Process 26455 attached with 20 threads > > % time seconds usecs/call calls errors syscall > > ------ ----------- ----------- --------- --------- ---------------- > > 99.80 11245.498406 42527 264435 130887 futex > > 0.09 10.480000 3493333 3 fsync > > 0.08 8.886784 0 39275508 read > > 0.02 2.552284 0 16397440 write > > 0.00 0.367716 0 50708676 lseek > > ------ ----------- ----------- --------- --------- ---------------- > > 100.00 11267.833632 106646970 130895 total > > ? > > > > ?Pretty damaging for futex: almost half of the calls went wrong and 99.8% > > of the time is spend there?. > > > > ?I have some finding out to do.? > > > I'm not sure this is damning for futex. You said you are not creating > threads yourself, which means you probably only have one I/O bound thread > actually doing anything. The other 19 threads are presumably spawned by the > APIs you are using and are likely just waiting for something to do. jstack > <PID> will give you details on each thread in the JVM so you can see what > they are up to. > > It's not like the futex calls are wasting CPU (in this case) - the threads > are idle until the kernel wakes them up. >
?99.8 percent of the time is spend on futex. That seems a tad much. -- Cecil Westerhof
