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SubjectRe: [PATCH v8 2/2] nohz: set isolcpus when nohz_full is set
On Tue, Apr 14, 2015 at 11:17:55AM -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.
>
> Acked-by: Frederic Weisbecker <fweisbec@gmail.com>

No need to put my ack, since I'll add my Signed-off-by when I apply the patches.
Note this won't go through this merge window though as we are in the middle of
it already.

Peter, are you ok with these two patches?

Thanks.

> Acked-by: Mike Galbraith <umgwanakikbuti@gmail.com> ["thumbs up!"]
> Acked-by: Rik van Riel <riel@redhat.com>
> Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com>
> ---
> v8: no change in this patch, just in 1/2
> Add Frederic's Ack
>
> 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]
>
> v2: add Mike and Rik's Acked-by
>
> 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);
> +
> sched_init_numa();
>
> /*
> --
> 2.1.2
>


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