From: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
To: Ingo Molnar <mingo@kernel.org>, Peter Zijlstra <peterz@infradead.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Mel Gorman <mgorman@techsingularity.net>,
Rik van Riel <riel@redhat.com>,
Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Subject: [PATCH] sched: Fix numabalancing to work with isolated cpus
Date: Tue, 4 Apr 2017 22:57:28 +0530 [thread overview]
Message-ID: <1491326848-5748-1-git-send-email-srikar@linux.vnet.ibm.com> (raw)
When performing load balancing, numabalancing only looks at
task->cpus_allowed to see if the task can run on the target cpu. If
isolcpus kernel parameter is set, then isolated cpus will not be part of
mask task->cpus_allowed.
For example: (On a Power 8 box running in smt 1 mode)
isolcpus=56,64,72,80,88
Cpus_allowed_list: 0-55,57-63,65-71,73-79,81-87,89-175
/proc/20996/task/20996/status:Cpus_allowed_list: 0-55,57-63,65-71,73-79,81-87,89-175
/proc/20996/task/20997/status:Cpus_allowed_list: 0-55,57-63,65-71,73-79,81-87,89-175
/proc/20996/task/20998/status:Cpus_allowed_list: 0-55,57-63,65-71,73-79,81-87,89-175
Note: offline cpus are excluded in cpus_allowed_list.
However a task might call sched_setaffinity() that includes all possible
cpus in the system including the isolated cpus.
For example:
perf bench numa mem --no-data_rand_walk -p 4 -t $THREADS -G 0 -P 3072 -T 0 -l 50 -c -s 1000
would call sched_setaffinity that resets the cpus_allowed mask.
Cpus_allowed_list: 0-55,57-63,65-71,73-79,81-87,89-175
Cpus_allowed_list: 0,8,16,24,32,40,48,56,64,72,80,88,96,104,112,120,128,136,144,152,160,168
Cpus_allowed_list: 0,8,16,24,32,40,48,56,64,72,80,88,96,104,112,120,128,136,144,152,160,168
Cpus_allowed_list: 0,8,16,24,32,40,48,56,64,72,80,88,96,104,112,120,128,136,144,152,160,168
Cpus_allowed_list: 0,8,16,24,32,40,48,56,64,72,80,88,96,104,112,120,128,136,144,152,160,168
The isolated cpus are part of the cpus allowed list. In the above case,
numabalancing ends up scheduling some of these tasks on isolated cpus.
To avoid this, please check for isolated cpus before choosing a target
cpu.
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
---
kernel/sched/fair.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index f045a35..f853dc0 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1666,6 +1666,10 @@ static void task_numa_find_cpu(struct task_numa_env *env,
if (!cpumask_test_cpu(cpu, &env->p->cpus_allowed))
continue;
+ /* Skip isolated cpus */
+ if (cpumask_test_cpu(cpu, cpu_isolated_map))
+ continue;
+
env->dst_cpu = cpu;
task_numa_compare(env, taskimp, groupimp);
}
--
1.8.3.1
next reply other threads:[~2017-04-04 17:27 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-04 17:27 Srikar Dronamraju [this message]
2017-04-04 18:56 ` [PATCH] sched: Fix numabalancing to work with isolated cpus Rik van Riel
2017-04-04 20:37 ` Mel Gorman
2017-04-05 1:50 ` Srikar Dronamraju
2017-04-05 8:09 ` Mel Gorman
2017-04-05 12:57 ` Michal Hocko
2017-04-05 15:22 ` Srikar Dronamraju
2017-04-05 16:44 ` Michal Hocko
2017-04-06 7:19 ` Srikar Dronamraju
2017-04-06 7:34 ` Michal Hocko
2017-04-06 9:23 ` Peter Zijlstra
2017-04-06 10:13 ` Michal Hocko
2017-04-06 10:29 ` Peter Zijlstra
2017-04-06 10:42 ` Michal Hocko
2017-04-06 10:47 ` Peter Zijlstra
2017-04-06 13:44 ` Michal Hocko
2017-04-06 7:36 ` Mike Galbraith
2017-04-06 7:36 ` Peter Zijlstra
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1491326848-5748-1-git-send-email-srikar@linux.vnet.ibm.com \
--to=srikar@linux.vnet.ibm.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mgorman@techsingularity.net \
--cc=mingo@kernel.org \
--cc=peterz@infradead.org \
--cc=riel@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.