linux-kernel - [PATCH -v2 0/2] cpusets,isolcpus: resolve conflict between cpusets and isolcpus

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Message-Id: <1424882288-2910-1-git-send-email-riel@redhat.com>
Date:	Wed, 25 Feb 2015 11:38:06 -0500
From:	riel@...hat.com
To:	linux-kernel@...r.kernel.org
Subject: [PATCH -v2 0/2] cpusets,isolcpus: resolve conflict between cpusets and isolcpus

-v2 addresses the conflict David Rientjes spotted between my previous
patches and commit e8e6d97c9b ("cpuset: use %*pb[l] to print bitmaps
including cpumasks and nodemasks")

Ensure that cpus specified with the isolcpus= boot commandline
option stay outside of the load balancing in the kernel scheduler.

Operations like load balancing can introduce unwanted latencies,
which is exactly what the isolcpus= commandline is there to prevent.

Previously, simply creating a new cpuset, without even touching the
cpuset.cpus field inside the new cpuset, would undo the effects of
isolcpus=, by creating a scheduler domain spanning the whole system,
and setting up load balancing inside that domain. The cpuset root
cpuset.cpus file is read-only, so there was not even a way to undo
that effect.

This does not impact the majority of cpusets users, since isolcpus=
is a fairly specialized feature used for realtime purposes.

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