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

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Message-Id: <1361550275-5716-1-git-send-email-nzimmer@sgi.com>
Date:	Fri, 22 Feb 2013 10:24:33 -0600
From:	Nathan Zimmer <nzimmer@....com>
To:	viresh.kumar@...aro.org, rjw@...k.pl
Cc:	cpufreq@...r.kernel.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, Nathan Zimmer <nzimmer@....com>
Subject: [PATCH v4 0/2] cpufreq: cpufreq_driver_lock is hot on large systems

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(-)

-- 
1.8.1.2

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