Messages in this thread Patch in this message | | | From | Barry Song <> | Subject | [PATCH v3] sched/fair: Eliminate confusion for the scan number in select_idle_cpu | Date | Fri, 26 Nov 2021 18:51:39 +0800 |
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From: Barry Song <song.bao.hua@hisilicon.com>
Right now, the number of scans is very confusing. For example, if nr==4, the code is iterating 4 times but scanning 3 times only. Because in the 4th iteration, the code returns directly due to --nr==0. So the code is wasting time on doing the 4th cpumask_next_wrap() and it is also very confusing since the actual scan number is nr-1 but not nr. This seems not to be the original intention.
This patch moves to scan nr times rather than nr-1 times, and it also makes the last iteration of cpumask_next_wrap() useful.
Signed-off-by: Barry Song <song.bao.hua@hisilicon.com> --- -v3: scan nr times instead of nr-1 times with respect to Peter's comments; rewrite commit log and subject since we have changed the behaviour of the code; -v2: https://lore.kernel.org/lkml/20211124091546.5072-1-21cnbao@gmail.com/
kernel/sched/fair.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 6e476f6..5c259aa 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6285,11 +6285,11 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, bool return i; } else { - if (!--nr) - return -1; idle_cpu = __select_idle_cpu(cpu, p); if ((unsigned int)idle_cpu < nr_cpumask_bits) break; + if (!--nr) + return -1; } } -- 1.8.3.1
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