Date: Thu, 3 Sep 2009 14:10:45 +0200
From: Andreas Herrmann <andreas.herrmann3@amd.com>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
CC: Ingo Molnar <mingo@elte.hu>, linux-kernel@vger.kernel.org,
       Gautham R Shenoy <ego@in.ibm.com>, Balbir Singh <balbir@in.ibm.com>
Subject: Re: [RFC][PATCH 0/8] load-balancing and cpu_power -v2
Message-ID: <20090903121045.GK7216@alberich.amd.com>
References: <20090901083431.748830771@chello.nl>
MIME-Version: 1.0
Content-Type: text/plain; charset="iso-8859-1"
Content-Disposition: inline
In-Reply-To: <20090901083431.748830771@chello.nl>
User-Agent: Mutt/1.5.16 (2007-06-09)
Content-Transfer-Encoding: 8BIT
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1917
Lines: 52

On Tue, Sep 01, 2009 at 10:34:31AM +0200, Peter Zijlstra wrote:
> A more complete version, one that compiles and mostly works on the
> simple tests to which it was subjected.
> 
> It still lacks integration with APERF/MPERF because that stuff was
> hidding in some acpi driver instead of placed in arch code for general
> consumption.. will fix.
> 
> Also, SD_SHARE_CPUPOWER seems redundant in the face of sd->level ==
> SD_LV_SIBLING, should we remove the SD_flag or depricate the level?
> 
> Anyway, have at it, poke holes and report issues.

Tested it (to a certain extend).
Found no performance degradation (on 1P, 2P, 4P systems). (One could
think performance might slightly degrade due to more frequent
__cpu_power updates).

Issue that I see is that switching between scheduling policies has no
effect on already running tasks:

- tasks that are already distributed among sockets are _not_
  concentrated on one socket when switching from performance to
  power_savings scheduling

- tasks utilizing a socket are _not_ distributed among sockets when
  switching from power_savings to performance policy

This applies to modification of sched_mc_power_savings. And I think
one of above scenarios is already broken in tip/master w/o your
patches.

Otherwise especially wrt to integration of APERF/MPERF this seems to
be a good approach.


Regards,
Andreas

-- 
Operating | Advanced Micro Devices GmbH
  System  | Karl-Hammerschmidt-Str. 34, 85609 Dornach b. M?nchen, Germany
 Research | Gesch?ftsf?hrer: Andrew Bowd, Thomas M. McCoy, Giuliano Meroni
  Center  | Sitz: Dornach, Gemeinde Aschheim, Landkreis M?nchen
  (OSRC)  | Registergericht M?nchen, HRB Nr. 43632


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/