Messages in this thread | | | Date | Tue, 31 Oct 2023 16:39:28 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH v3] sched/fair: Fix the decision for load balance |
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On Tue, Oct 31, 2023 at 02:38:22PM +0100, Keisuke Nishimura wrote: > should_we_balance is called for the decision to do load-balancing. > When sched ticks invoke this function, only one CPU should return > true. However, in the current code, two CPUs can return true. The > following situation, where b means busy and i means idle, is an > example, because CPU 0 and CPU 2 return true. > > [0, 1] [2, 3] > b b i b > > This fix checks if there exists an idle CPU with busy sibling(s) > after looking for a CPU on an idle core. If some idle CPUs with busy > siblings are found, just the first one should do load-balancing. > > Fixes: b1bfeab9b002 ("sched/fair: Consider the idle state of the whole core for load balance") > Signed-off-by: Keisuke Nishimura <keisuke.nishimura@inria.fr> > Reviewed-by: Chen Yu <yu.c.chen@intel.com> > Reviewed-by: Shrikanth Hegde <sshegde@linux.vnet.ibm.com> > Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
I'll sit on this until after the merge window, but then I'll queue it for sched/urgent.
Thanks!
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