linux-kernel - Re: Restricting Processor Usage

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Message-Id: <200805092128.56917.ioe-lkml@rameria.de>
Date:	Fri, 9 May 2008 21:28:56 +0200
From:	Ingo Oeser <ioe-lkml@...eria.de>
To:	Brian McGrew <brian@...ionpro.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Restricting Processor Usage

Hi Brian
On Friday 09 May 2008, you wrote:
> Now that I've got sched_(set|get)affinity working (thank you all for all of
> the great help), I need to figure out how to unload the processors in the
> machine.

excerpt from Documentation/kernel-parameters.txt:

        isolcpus=       [KNL,SMP] Isolate CPUs from the general scheduler.
                        Format:
                        <cpu number>,...,<cpu number>
                        or
                        <cpu number>-<cpu number>  (must be a positive range in ascending order)
                        or a mixture
                        <cpu number>,...,<cpu number>-<cpu number>
                        This option can be used to specify one or more CPUs
                        to isolate from the general SMP balancing and scheduling
                        algorithms. The only way to move a process onto or off
                        an "isolated" CPU is via the CPU affinity syscalls.
                        <cpu number> begins at 0 and the maximum value is
                        "number of CPUs in system - 1".

                        This option is the preferred way to isolate CPUs. The
                        alternative -- manually setting the CPU mask of all
                        tasks in the system -- can cause problems and
                        suboptimal load balancer performance.

And then use sched_set_affinity to fill your CPUs.

Happy imaging :-)


Best Regards

Ingo Oeser
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