linux-kernel - Re: [RFC PATCH v2 0/7] Tunable sched_mc_power

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Message-ID: <20080908135834.GH26079@one.firstfloor.org>
Date:	Mon, 8 Sep 2008 15:58:34 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Suresh B Siddha <suresh.b.siddha@...el.com>,
	Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>,
	Ingo Molnar <mingo@...e.hu>,
	Dipankar Sarma <dipankar@...ibm.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Vatsa <vatsa@...ux.vnet.ibm.com>,
	Gautham R Shenoy <ego@...ibm.com>,
	Andi Kleen <andi@...stfloor.org>,
	David Collier-Brown <davecb@....com>,
	Tim Connors <tconnors@...ro.swin.edu.au>,
	Max Krasnyansky <maxk@...lcomm.com>
Subject: Re: [RFC PATCH v2 0/7] Tunable sched_mc_power_savings=n

> 1. Detailed documentation

Messy code cannot be really made good with documentation. It's
not that your patches are that messy, it's more that it makes
something already overcomplicated even worse.

> 2. Cleanup the group_min and group_leader stuff in
>    find_busiest_group()

I think one issue is that there are general too many special cases
that completely change the algorithm especially for power saving.
Perhaps it would make sense to refactor the code a bit and then
use different high level code paths for those?  I assume that
would make it all simpler and easier to understand.

The other alternative would be to dynamically change the domains
so that a generic graph walker without knowledge of power savings
could DTRT in all cases. But I assume that would be much harder.

-Andi

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