Messages in this thread Patch in this message | | | From | Jirka Hladky <> | Date | Wed, 13 May 2020 18:20:53 +0200 | Subject | Re: [PATCH 00/13] Reconcile NUMA balancing decisions with the load balancer v6 |
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Thank you, Mel!
I think I have to make sure we cover the scenario you have targeted when developing adjust_numa_imbalance:
======================================================================= https://github.com/torvalds/linux/blob/4f8a3cc1183c442daee6cc65360e3385021131e4/kernel/sched/fair.c#L8910
/* * Allow a small imbalance based on a simple pair of communicating * tasks that remain local when the source domain is almost idle. */ =======================================================================
Could you point me to a benchmark for this scenario? I have checked https://github.com/gormanm/mmtests and we use lots of the same benchmarks but I'm not sure if we cover this particular scenario.
Jirka
On Wed, May 13, 2020 at 5:30 PM Mel Gorman <mgorman@techsingularity.net> wrote: > > On Wed, May 13, 2020 at 04:57:15PM +0200, Jirka Hladky wrote: > > Hi Mel, > > > > we have tried the kernel with adjust_numa_imbalance() crippled to just > > return the imbalance it's given. > > > > It has solved all the performance problems I have reported. > > Performance is the same as with 5.6 kernel (before the patch was > > applied). > > > > * solved the performance drop upto 20% with single instance > > SPECjbb2005 benchmark on 8 NUMA node servers (particularly on AMD EPYC > > Rome systems) => this performance drop was INCREASING with higher > > threads counts (10% for 16 threads and 20 % for 32 threads) > > * solved the performance drop for low load scenarios (SPECjvm2008 and NAS) > > > > Any suggestions on how to proceed? One approach is to turn > > "imbalance_min" into the kernel tunable. Any other ideas? > > > > https://github.com/torvalds/linux/blob/4f8a3cc1183c442daee6cc65360e3385021131e4/kernel/sched/fair.c#L8914 > > > > Complete shot in the dark but restore adjust_numa_imbalance() and try > this > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 1a9983da4408..0b31f4468d5b 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -2393,7 +2393,7 @@ static void ttwu_queue(struct task_struct *p, int cpu, int wake_flags) > struct rq_flags rf; > > #if defined(CONFIG_SMP) > - if (sched_feat(TTWU_QUEUE) && !cpus_share_cache(smp_processor_id(), cpu)) { > + if (sched_feat(TTWU_QUEUE)) { > sched_clock_cpu(cpu); /* Sync clocks across CPUs */ > ttwu_queue_remote(p, cpu, wake_flags); > return; > > -- > Mel Gorman > SUSE Labs >
-- -Jirka
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