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. -Rowan
