linux-kernel - [RFC] cpuset: Explicit dynamic sched domain cpuset flag

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Message-ID: <20061030212922.GA20369@in.ibm.com>
Date:	Tue, 31 Oct 2006 02:59:22 +0530
From:	Dinakar Guniguntala <dino@...ibm.com>
To:	Paul Jackson <pj@....com>
Cc:	nickpiggin@...oo.com.au, akpm@...l.org, mbligh@...gle.com,
	menage@...gle.com, Simon.Derr@...l.net,
	linux-kernel@...r.kernel.org, rohitseth@...gle.com, holt@....com,
	dipankar@...ibm.com, suresh.b.siddha@...el.com
Subject: [RFC] cpuset:  Explicit dynamic sched domain cpuset flag

Hi,

The existing cpuset code that partitioned sched domains at the
back of a exclusive cpuset has one major problem. Administrators
will find that tasks assigned to top level cpusets, that contain
child cpusets that are exclusive, can no longer be rebalanced across
the entire cpus_allowed mask. It was felt that instead of overloading
the cpu_exclusive flag to also create sched domains, it would be
better to have a separate flag that denotes a sched domain. That
way the admins have the flexibility to create exclusive cpusets
that do not necessarily define sched domains.

This patch adds a new flag sched_domain. This can only be set on a
cpu_exclusive cpuset. If set then, the sched domain consists of all
CPUs in the current cpuset that are not part of any exclusive child
cpusets that also define sched domains.

However there are 2 additional extensions that may need to be
looked into
1. There is still no way to find the current sched domain
   configuration of the system on demand from userspace.
   (Apart from turning SCHED_DOMAIN_DEBUG on and checking dmesg)
2. A way to specify a NULL sched domain, ie mark an exclusive
   cpuset that defines a sched domain as one with no load balancing.
   This can be accomplished by adding yet another flag that says
   dont load balance (say no_load_balance)

Signed-off-by: Dinakar Guniguntala <dino@...ibm.com>

View attachment "add_sd.patch" of type "text/plain" (9261 bytes)