linux-kernel - Re: [PATCH v5 0/2] sched/numa: Skip VMA scanning on memory pinned to one NUMA node via cpuset.mems

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Message-ID: <98092a32-f903-49a3-a5b6-7edffa9edd55@amd.com>
Date: Thu, 24 Apr 2025 10:12:32 +0530
From: K Prateek Nayak <kprateek.nayak@....com>
To: Libo Chen <libo.chen@...cle.com>, <akpm@...ux-foundation.org>,
	<rostedt@...dmis.org>, <peterz@...radead.org>, <mgorman@...e.de>,
	<mingo@...hat.com>, <juri.lelli@...hat.com>, <vincent.guittot@...aro.org>,
	<tj@...nel.org>, <llong@...hat.com>
CC: <sraithal@....com>, <venkat88@...ux.ibm.com>, <raghavendra.kt@....com>,
	<yu.c.chen@...el.com>, <tim.c.chen@...el.com>, <vineethr@...ux.ibm.com>,
	<chris.hyser@...cle.com>, <daniel.m.jordan@...cle.com>,
	<lorenzo.stoakes@...cle.com>, <mkoutny@...e.com>, <linux-mm@...ck.org>,
	<cgroups@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 0/2] sched/numa: Skip VMA scanning on memory pinned to
 one NUMA node via cpuset.mems

Hello Libo,

On 4/24/2025 8:15 AM, Libo Chen wrote:
> v1->v2:
> 1. add perf improvment numbers in commit log. Yet to find perf diff on
> will-it-scale, so not included here. Plan to run more workloads.
> 2. add tracepoint.
> 3. To peterz's comment, this will make it impossible to attract tasks to
> those memory just like other VMA skippings. This is the current
> implementation, I think we can improve that in the future, but at the
> moment it's probabaly better to keep it consistent.

I tested the series with hackbench running on a dual socket system with
memory pinned to one node and I could see the skip_cpuset_numa traces
being logged:

  sched-messaging-9430    ...: sched_skip_cpuset_numa: comm=sched-messaging pid=9430 tgid=9007 ngid=0 mem_nodes_allowed=0
  sched-messaging-9640    ...: sched_skip_cpuset_numa: comm=sched-messaging pid=9640 tgid=9007 ngid=0 mem_nodes_allowed=0
  sched-messaging-9645    ...: sched_skip_cpuset_numa: comm=sched-messaging pid=9645 tgid=9007 ngid=0 mem_nodes_allowed=0
  sched-messaging-9637    ...: sched_skip_cpuset_numa: comm=sched-messaging pid=9637 tgid=9007 ngid=0 mem_nodes_allowed=0
  sched-messaging-9629    ...: sched_skip_cpuset_numa: comm=sched-messaging pid=9629 tgid=9007 ngid=0 mem_nodes_allowed=0
  sched-messaging-9639    ...: sched_skip_cpuset_numa: comm=sched-messaging pid=9639 tgid=9007 ngid=0 mem_nodes_allowed=0
  sched-messaging-9630    ...: sched_skip_cpuset_numa: comm=sched-messaging pid=9630 tgid=9007 ngid=0 mem_nodes_allowed=0
  sched-messaging-9487    ...: sched_skip_cpuset_numa: comm=sched-messaging pid=9487 tgid=9007 ngid=0 mem_nodes_allowed=0
  sched-messaging-9635    ...: sched_skip_cpuset_numa: comm=sched-messaging pid=9635 tgid=9007 ngid=0 mem_nodes_allowed=0
  sched-messaging-9647    ...: sched_skip_cpuset_numa: comm=sched-messaging pid=9647 tgid=9007 ngid=0 mem_nodes_allowed=0
  ...

Feel free to add:

Tested-by: K Prateek Nayak <kprateek.nayak@....com>

-- 
Thanks and Regards,
Prateek

> 
> v2->v3:
> 1. add enable_cpuset() based on Mel's suggestion but again I think it's
> redundant.
> 2. print out nodemask with %*p.. format in the tracepoint.
> 
> v3->v4:
> 1. fix an unsafe dereference of a pointer to content not on ring buffer,
> namely mem_allowed_ptr in the tracepoint.
> 
> v4->v5:
> 1. add BUILD_BUG_ON() in TP_fast_assign() to guard against future
> changes (particularly in size) in nodemask_t.
> 
> Libo Chen (2):
>    sched/numa: Skip VMA scanning on memory pinned to one NUMA node via
>      cpuset.mems
>    sched/numa: Add tracepoint that tracks the skipping of numa balancing
>      due to cpuset memory pinning
> 
>   include/trace/events/sched.h | 33 +++++++++++++++++++++++++++++++++
>   kernel/sched/fair.c          |  9 +++++++++
>   2 files changed, 42 insertions(+)
>