sched: do not count frozen tasks toward load
authorNathan Lynch <ntl@pobox.com>
Thu, 9 Apr 2009 00:45:12 +0000 (19:45 -0500)
committerIngo Molnar <mingo@elte.hu>
Thu, 9 Apr 2009 05:37:02 +0000 (07:37 +0200)
commite3c8ca8336707062f3f7cb1cd7e6b3c753baccdd
tree281917ab686d2e2a9e1a3996f729fbe97037de97
parent01fad98a1f1d3b38adcbab4bd97f7f4cb983ffb5
sched: do not count frozen tasks toward load

Freezing tasks via the cgroup freezer causes the load average to climb
because the freezer's current implementation puts frozen tasks in
uninterruptible sleep (D state).

Some applications which perform job-scheduling functions consult the
load average when making decisions.  If a cgroup is frozen, the load
average does not provide a useful measure of the system's utilization
to such applications.  This is especially inconvenient if the job
scheduler employs the cgroup freezer as a mechanism for preempting low
priority jobs.  Contrast this with using SIGSTOP for the same purpose:
the stopped tasks do not count toward system load.

Change task_contributes_to_load() to return false if the task is
frozen.  This results in /proc/loadavg behavior that better meets
users' expectations.

Signed-off-by: Nathan Lynch <ntl@pobox.com>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Nigel Cunningham <nigel@tuxonice.net>
Tested-by: Nigel Cunningham <nigel@tuxonice.net>
Cc: <stable@kernel.org>
Cc: containers@lists.linux-foundation.org
Cc: linux-pm@lists.linux-foundation.org
Cc: Matt Helsley <matthltc@us.ibm.com>
LKML-Reference: <20090408194512.47a99b95@manatee.lan>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
include/linux/sched.h