sched: fix nohz load balancer on cpu offline

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Christian Borntraeger reports:

> After a logical cpu offline, even on a complete idle system, there
> is one cpu with full ticks. It turns out that nohz.cpu_mask has the
> the offlined cpu still set.
>
> In select_nohz_load_balancer() we check if the system is completely
> idle to turn of load balancing. We compare cpu_online_map with
> nohz.cpu_mask.  Since cpu_online_map is updated on cpu unplug,
> but nohz.cpu_mask is not, the check fails and the scheduler believes
> that we need an "idle load balancer" even on a fully idle system.
> Since the ilb cpu does not deactivate the timer tick this breaks NOHZ.

Fix the select_nohz_load_balancer() to not set the nohz.cpu_mask
while a cpu is going offline.

Reported-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Tested-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

...

This commit is contained in:

Suresh Siddha 2009-02-04 11:59:44 -08:00 • committed by Ingo Molnar

parent 35626129ab

commit 483b4ee60e

1 changed files with 11 additions and 6 deletions

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kernel/sched.c

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