Re: [patch] CFS scheduler, -v19

Ian Kent
2007-07-17T05:01:30Z

On Mon, 2007-07-16 at 23:55 +0200, Ingo Molnar wrote:
> * Chuck Ebbert <cebbert@redhat.com> wrote:
>
> > On 07/13/2007 05:19 PM, Bill Davidsen wrote:
> > >
> > > I should really go back to 2.6.21.6, 2.6.22 has many bizarre behaviors
> > > with FC6. Automount starts taking 30% of CPU (unused at the moment)
> >
> > Can you confirm whether CFS is involved, i.e. does it spin like that
> > even without the CFS patch applied?
>
> hmmm .... could you take out the kernel/time.c (sys_time()) changes from
> the CFS patch, does that solve the automount issue? If yes, could
> someone take a look at automount and check whether it makes use of
> time(2) and whether it combines it with finer grained time sources?

Yes it does and I have two reported bugs so far.

In several places I have code similar to:

wait.tv_sec = time(NULL) + 1;
wait.tv_nsec = 0;

signaled = 0;
while (!signaled) {
status = pthread_cond_timedwait(&cond, &mutex, &wait);
if (status) {
if (status == ETIMEDOUT)
break;
fatal(status);
}
}

lead to automount spinning with strace output a bit like:

futex(0x80034b60, FUTEX_WAKE, 1) = 0
clock_gettime(CLOCK_REALTIME, {1184593936, 130925919}) = 0
time(NULL) = 1184593935
futex(0x80034b60, FUTEX_WAKE, 1) = 0
clock_gettime(CLOCK_REALTIME, {1184593936, 131160876}) = 0
time(NULL) = 1184593935
futex(0x80034b60, FUTEX_WAKE, 1) = 0
clock_gettime(CLOCK_REALTIME, {1184593936, 131377080}) = 0
time(NULL) = 1184593935
futex(0x80034b60, FUTEX_WAKE, 1) = 0
clock_gettime(CLOCK_REALTIME, {1184593936, 131593297}) = 0
time(NULL) = 1184593935
futex(0x80034b60, FUTEX_WAKE, 1) = 0
clock_gettime(CLOCK_REALTIME, {1184593936, 131871792}) = 0

There should be something like:

futex(0x5555557868c4, FUTEX_WAIT, 5321099, {0, 998091311}) = -1 ETIMEDOUT (Connection timed out)

in there I think.

Ian