On Sun, 16 Aug 2015, Sebastian Andrzej Siewior wrote: > * Thomas Gleixner | 2015-08-04 14:05:10 [+0200]: > > >On Tue, 4 Aug 2015, Nicholas Mc Guire wrote: > >> <snip> > >> 3 root -2 0 0 0 0 R 60.3 0.0 5756:16 ksoftirqd/0 > >> 23 root -2 0 0 0 0 R 50.8 0.0 4948:08 ksoftirqd/2 > >> 17 root -2 0 0 0 0 S 50.6 0.0 4897:13 ksoftirqd/1 > >> 29 root -2 0 0 0 0 S 50.4 0.0 4953:24 ksoftirqd/3 > > > >So ksoftirqd eats 50+% CPU on each core. On an idle system!?! Any > >chance that you can get a function trace snapshot out of it? > > This might be a .config thing, device driver or user land behaviour. > Usually ksoftirqd should remain (almost) idle because most of BH work > remains in task-context and not in ksoftirqd. tasklets for instance > should run in ksoftirqd. So a function trace or event tracing to figure > out what is scheduling the softirq might give a pointer. > I have here a AMD box with > > 3 root -2 0 0 0 0 S 1.3 0.0 126:16.31 ksoftirqd/0 > 18 root -2 0 0 0 0 S 1.3 0.0 136:55.85 ksoftirqd/1 > 30 root -2 0 0 0 0 S 1.3 0.0 138:50.52 ksoftirqd/3 > 24 root -2 0 0 0 0 S 1.0 0.0 143:54.28 ksoftirqd/2 > > with a 15 days uptime. That one percent CPU usage on a idle system looks > odd here, too. Not really. If ksoftirqd takes 13us per invocation and you run with HZ=1000 then this is reasonable. Thanks, tglx -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
