From: Rik van Riel <riel@redhat.com>
To: Arjan van de Ven <arjan@linux.intel.com>
Cc: linux-kernel@vger.kernel.org, "Rafael J. Wysocki" <rjw@sisk.pl>,
ShuoX Liu <shuox.liu@intel.com>,
mjg59@srcf.ucam.org, Boris Ostrovsky <boris.ostrovsky@amd.com>,
Len Brown <len.brown@intel.com>,
Deepthi Dharwar <deepthi@linux.vnet.ibm.com>
Subject: Re: [RFC][PATCH 0/3] c-state governor changes
Date: Thu, 23 Aug 2012 22:57:27 -0400 [thread overview]
Message-ID: <5036ED97.8040306@redhat.com> (raw)
In-Reply-To: <5036A67D.9090904@linux.intel.com>
On 08/23/2012 05:54 PM, Arjan van de Ven wrote:
> On 8/23/2012 2:11 PM, Rik van Riel wrote:
>> This patch set is mostly there to kick off a discussion in time
>> for Kernel Summit. When running it on my laptop, with acpi_idle,
>> I see a promising change in powertop.
>
> be careful with acpi_idle... that will remove most of the intermediate C states the platform has,
> so the policy engine no longer has good things to chose from.
Interesting, I was not aware of that.
Another thing I did see is that the intel_idle driver selects
a target residency time around 4x larger than the exit latency
for most c-states, while acpi_idle sticks to 2x by default.
Aiming for a residency time only 2x the exit latency seems
excessively aggressive, especially for the deeper c states.
The latency issues with various KVM guests communicating with
each other have been observed on various Intel and AMD chipsets,
not unique to one vendor.
--
All rights reversed
next prev parent reply other threads:[~2012-08-24 2:57 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-23 21:11 [RFC][PATCH 0/3] c-state governor changes Rik van Riel
2012-08-23 21:11 ` [RFC][PATCH 1/3] cpuidle: fix underflow in stddev calculation Rik van Riel
2012-08-23 21:13 ` [RFC][PATCH 2/3] cpuidle: find a typical recent sleep interval Rik van Riel
2012-08-23 21:13 ` [RFC][PATCH 3/3] cpuidle: count double the exit latency Rik van Riel
2012-08-23 21:54 ` [RFC][PATCH 0/3] c-state governor changes Arjan van de Ven
2012-08-24 2:57 ` Rik van Riel [this message]
2012-08-24 4:11 ` Matthew Garrett
2012-08-23 21:54 ` Arjan van de Ven
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