From: Mel Gorman <mgorman@techsingularity.net>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Vincent Guittot <vincent.guittot@linaro.org>,
Ingo Molnar <mingo@kernel.org>,
Juri Lelli <juri.lelli@redhat.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>,
Valentin Schneider <valentin.schneider@arm.com>,
Phil Auld <pauld@redhat.com>, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 08/11] sched/numa: Bias swapping tasks based on their preferred node
Date: Thu, 13 Feb 2020 11:18:02 +0000 [thread overview]
Message-ID: <20200213111802.GW3466@techsingularity.net> (raw)
In-Reply-To: <20200213103108.GG14914@hirez.programming.kicks-ass.net>
On Thu, Feb 13, 2020 at 11:31:08AM +0100, Peter Zijlstra wrote:
> On Wed, Feb 12, 2020 at 09:36:51AM +0000, Mel Gorman wrote:
> > When swapping tasks for NUMA balancing, it is preferred that tasks move
> > to or remain on their preferred node. When considering an imbalance,
> > encourage tasks to move to their preferred node and discourage tasks from
> > moving away from their preferred node.
>
> Wasn't there an issue for workloads that span multiple nodes?
>
Sortof, yes -- specifically workloads that could not fit inside a node
for whatever reason.
> Say a 4 node system with 2 warehouses? Then each JVM will want 2 nodes,
> instead of a single node, and strong preferred node stuff makes it
> difficult to achieve this.
>
> I forgot how we dealt with these cases, just something I worry about
> when reading this.
We deal with it in task_numa_migrate() by considering nodes other
than the preferred node for placement -- see "Look at other nodes in
these cases" followed by a sched_setnuma if the preferred node doesn't
match.
We do not do any special casing as such in task_numa_compare other than
finding the best improvement so we can pick a task belonging to a group
spanning multiple nodes with or without this patch. A workload spanning
multiple nodes in itself does not justify a full search if it can be
avoided.
--
Mel Gorman
SUSE Labs
next prev parent reply other threads:[~2020-02-13 11:18 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-12 9:36 [RFC PATCH 00/11] Reconcile NUMA balancing decisions with the load balancer Mel Gorman
2020-02-12 9:36 ` [PATCH 01/11] sched/fair: Allow a small load imbalance between low utilisation SD_NUMA domains Mel Gorman
2020-02-12 9:36 ` [PATCH 02/11] sched/fair: Optimize select_idle_core() Mel Gorman
2020-02-12 9:36 ` [PATCH 03/11] sched/fair: Allow a per-CPU kthread waking a task to stack on the same CPU, to fix XFS performance regression Mel Gorman
2020-02-12 9:36 ` [PATCH 04/11] sched/numa: Trace when no candidate CPU was found on the preferred node Mel Gorman
2020-02-12 9:36 ` [PATCH 05/11] sched/numa: Distinguish between the different task_numa_migrate failure cases Mel Gorman
2020-02-12 14:43 ` Steven Rostedt
2020-02-12 15:59 ` Mel Gorman
2020-02-12 9:36 ` [PATCH 06/11] sched/numa: Prefer using an idle cpu as a migration target instead of comparing tasks Mel Gorman
2020-02-12 9:36 ` [PATCH 07/11] sched/numa: Find an alternative idle CPU if the CPU is part of an active NUMA balance Mel Gorman
2020-02-12 9:36 ` [PATCH 08/11] sched/numa: Bias swapping tasks based on their preferred node Mel Gorman
2020-02-13 10:31 ` Peter Zijlstra
2020-02-13 11:18 ` Mel Gorman [this message]
2020-02-12 13:22 ` [RFC PATCH 00/11] Reconcile NUMA balancing decisions with the load balancer Vincent Guittot
2020-02-12 14:07 ` Valentin Schneider
2020-02-12 15:48 ` Mel Gorman
2020-02-12 16:13 ` Vincent Guittot
2020-02-12 15:45 ` [PATCH 09/11] sched/fair: Split out helper to adjust imbalances between domains Mel Gorman
2020-02-12 15:46 ` [PATCH 10/11] sched/numa: Use similar logic to the load balancer for moving between domains with spare capacity Mel Gorman
2020-02-12 15:46 ` [PATCH 11/11] sched/numa: Use similar logic to the load balancer for moving between overloaded domains Mel Gorman
[not found] ` <20200214041232.18904-1-hdanton@sina.com>
2020-02-14 7:50 ` [PATCH 08/11] sched/numa: Bias swapping tasks based on their preferred node Mel Gorman
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