Re: [PATCH] sched:Prefer numa hotness over cache hotness

From: Peter Zijlstra
Date: Thu Jun 11 2015 - 10:01:41 EST


On Wed, Jun 10, 2015 at 12:33:35PM +0530, Srikar Dronamraju wrote:
> The current load balancer may not try to prevent a task from moving out
> of a preferred node to a less preferred node. The reason for this being:
>
> - Since sched features NUMA and NUMA_RESIST_LOWER are disabled by
> default, migrate_degrades_locality() always returns false.
>
> - Even if NUMA_RESIST_LOWER were to be enabled, if its cache hot,
> migrate_degrades_locality() never gets called.
>
> The above behaviour can mean that tasks can move out of their preferred
> node but they may be eventually be brought back to their preferred node
> by numa balancer (due to higher numa faults).
>
> To avoid the above, this commit merges migrate_degrades_locality() and
> migrate_improves_locality(). It also replaces 3 sched features NUMA,
> NUMA_FAVOUR_HIGHER and NUMA_RESIST_LOWER by a single sched feature NUMA.
>

Does not apply.
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