Messages in this thread | | | Date | Fri, 17 Jan 2020 14:15:03 +0000 | From | Mel Gorman <> | Subject | Re: [PATCH] sched, fair: Allow a small load imbalance between low utilisation SD_NUMA domains v4 |
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On Fri, Jan 17, 2020 at 02:08:13PM +0100, Vincent Guittot wrote: > > > This patch allows a fixed degree of imbalance of two tasks to exist > > > between NUMA domains regardless of utilisation levels. In many cases, > > > this prevents communicating tasks being pulled apart. It was evaluated > > > whether the imbalance should be scaled to the domain size. However, no > > > additional benefit was measured across a range of workloads and machines > > > and scaling adds the risk that lower domains have to be rebalanced. While > > > this could change again in the future, such a change should specify the > > > use case and benefit. > > > > > > > Any thoughts on whether this is ok for tip or are there suggestions on > > an alternative approach? > > I have just finished to run some tests on my system with your patch > and I haven't seen any noticeable any changes so far which was a bit > expected. The tests that I usually run, use more than 4 tasks on my 2 > nodes system;
This is indeed expected. With more active tasks, normal load balancing applies.
> the only exception is perf sched pipe and the results > for this test stays the same with and without your patch.
I never saw much difference with perf sched pipe either. It was generally within the noise.
> I'm curious > if this impacts Phil's tests which run LU.c benchmark with some > burning cpu tasks
I didn't see any problem with LU.c whether parallelised by openMPI or openMP but an independent check would be nice.
-- Mel Gorman SUSE Labs
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