linux-kernel - Re: [PATCH v4 0/2] cpufreq: cpufreq_driver

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Message-ID: <3505617.pgqBjPDzlA@vostro.rjw.lan>
Date:	Tue, 12 Mar 2013 00:23:08 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Nathan Zimmer <nzimmer@....com>
Cc:	viresh.kumar@...aro.org, cpufreq@...r.kernel.org,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 0/2] cpufreq: cpufreq_driver_lock is hot on large systems

On Friday, February 22, 2013 10:24:33 AM Nathan Zimmer wrote:
> I am noticing the cpufreq_driver_lock is quite hot.
> On an idle 512 system perf shows me most of the system time is spent on this
> lock.  This is quite significant as top shows 5% of time in system time.
> My solution was to first convert the lock to a rwlock and then to the rcu.
> 
> v2: Rebase
> 
> v3: Read the RCU documentation instead of skimming it.  Also I based on 
> git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git pm+acpi-3.9-rc1
> I assumed that was what you would prefer Rafael.
> 
> v4: Removed an unnecessary syncronize_rcu().
> 
> 
> Nathan Zimmer (2):
>   cpufreq: Convert the cpufreq_driver_lock to a rwlock
>   cpufreq: Convert the cpufreq_driver_lock to use the rcu
> 
>  drivers/cpufreq/cpufreq.c | 286 ++++++++++++++++++++++++++++++++++------------
>  1 file changed, 211 insertions(+), 75 deletions(-)

I'm going to take patch [1/2] for v3.10, but patch [2/2] still needs some
work it seems.  Is that correct?  If so, are you going to send an update?

Rafael


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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