Re: [PATCH 00/13] Reconcile NUMA balancing decisions with the load balancer v6

[Jirka Hladky]

> 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;

Hi Mel,

we have performance results for the proposed patch above ^^^.
Unfortunately, it hasn't helped the performance.

Jirka


On Wed, May 13, 2020 at 5:30 PM Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> 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