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@xxxxxxxxx>
---
include/linux/sched.h | 3 ++-
1 files changed, 2 insertions(+), 1 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 011db2f..f8af167 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -202,7 +202,8 @@ extern unsigned long long time_sync_thresh;
#define task_is_stopped_or_traced(task) \
((task->state & (__TASK_STOPPED | __TASK_TRACED)) != 0)
#define task_contributes_to_load(task) \
- ((task->state & TASK_UNINTERRUPTIBLE) != 0)
+ ((task->state & TASK_UNINTERRUPTIBLE) != 0 && \
+ (task->flags & PF_FROZEN) == 0)
#define __set_task_state(tsk, state_value) \
do { (tsk)->state = (state_value); } while (0)
--
1.6.0.6
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