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SubjectRe: [PATCH v7 2/2] nohz: set isolcpus when nohz_full is set
On Fri, Apr 10, 2015 at 04:53:52PM -0400, Chris Metcalf wrote:
> nohz_full is only useful with isolcpus also set, since otherwise the
> scheduler has to run periodically to try to determine whether to steal
> work from other cores.
>
> Accordingly, when booting with nohz_full=xxx on the command line, we
> should act as if isolcpus=xxx was also set, and set (or extend) the
> isolcpus set to include the nohz_full cpus.
>
> Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com>
> ---
> v7: oops, use add_cpus_to, not remove_cpus_from [Frederic]
>
> v6: back to just using a direct update, with the new names
>
> v5: test run of Frederic's proposal to use sched_isolated_map_add()
>
> v4: update accessor names to make them clearer [PeterZ]
>
> v3: update changelog language to avoid using unclear "implies" [PeterZ]
>
> kernel/sched/core.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index f0f831e8a345..4a5681b5a4fd 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -7031,6 +7031,9 @@ void __init sched_init_smp(void)
> alloc_cpumask_var(&non_isolated_cpus, GFP_KERNEL);
> alloc_cpumask_var(&fallback_doms, GFP_KERNEL);
>
> + /* nohz_full won't take effect without isolating the cpus. */
> + tick_nohz_full_add_cpus_to(cpu_isolated_map);
> +

I can't say I like this, but I can not come up with a better name.
So that patch is ok to me (if Peterz acks it) :-)

> sched_init_numa();
>
> /*
> --
> 2.1.2
>


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