linux-kernel - Re: [PATCH 04/23] sched: Change NODE sched

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Message-ID: <20110429140917.GD22001@alberich.amd.com>
Date:	Fri, 29 Apr 2011 16:09:17 +0200
From:	Andreas Herrmann <andreas.herrmann3@....com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
CC:	Ingo Molnar <mingo@...e.hu>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Anton Blanchard <anton@....ibm.com>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Venkatesh Pallipadi <venki@...gle.com>,
	Paul Turner <pjt@...gle.com>, Mike Galbraith <efault@....de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Heiko Carstens <heiko.carstens@...ibm.com>
Subject: Re: [PATCH 04/23] sched: Change NODE sched_domain group creation

On Thu, Apr 07, 2011 at 08:09:45AM -0400, Peter Zijlstra wrote:
> The NODE sched_domain is 'special' in that it allocates sched_groups
> per CPU, instead of sharing the sched_groups between all CPUs.
> 
> While this might have some benefits on large NUMA and avoid remote
> memory accesses when iterating the sched_groups, this does break
> current code that assumes sched_groups are shared between all
> sched_domains (since the dynamic cpu_power patches).
> 
> So refactor the NODE groups to behave like all other groups.
> 
> (The ALLNODES domain again shared its groups across the CPUs for some
> reason).
> 
> If someone does measure a performance decrease due to this change we

[...]

Will do some performance sniff tests to check this.


Andreas

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