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authorSuresh Siddha <suresh.b.siddha@intel.com>2009-02-04 20:59:44 +0100
committerIngo Molnar <mingo@elte.hu>2009-02-04 22:31:19 +0100
commit483b4ee60edbefdfbff0dd538fb81f368d9e7c0d (patch)
tree2fbf152e6bb6377a16a1fb0d1aa503d19e0c0f63 /init/Kconfig
parentsched: add missing kernel-doc in sched.h (diff)
downloadlinux-483b4ee60edbefdfbff0dd538fb81f368d9e7c0d.tar.xz
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sched: fix nohz load balancer on cpu offline
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>
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