From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gautham R Shenoy Subject: Re: [PATCH v6 2/5] cpufreq: powernv: Remove cpu_to_chip_id() from hot-path Date: Mon, 25 Jan 2016 11:08:05 +0530 Message-ID: <20160125053804.GA5599@in.ibm.com> References: <1453447145-17722-1-git-send-email-shilpa.bhat@linux.vnet.ibm.com> <1453447145-17722-3-git-send-email-shilpa.bhat@linux.vnet.ibm.com> <20160123195920.552990ed@cotter.ozlabs.ibm.com> Reply-To: ego@linux.vnet.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from e31.co.us.ibm.com ([32.97.110.149]:48854 "EHLO e31.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751087AbcAYFiP (ORCPT ); Mon, 25 Jan 2016 00:38:15 -0500 Received: from localhost by e31.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Sun, 24 Jan 2016 22:38:14 -0700 Content-Disposition: inline In-Reply-To: <20160123195920.552990ed@cotter.ozlabs.ibm.com> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Balbir Singh Cc: Shilpasri G Bhat , linuxppc-dev@ozlabs.org, linux-kernel@vger.kernel.org, rjw@rjwysocki.net, viresh.kumar@linaro.org, linux-pm@vger.kernel.org, pc@us.ibm.com, anton@samba.org, ego@linux.vnet.ibm.com, shreyas@linux.vnet.ibm.com Hello Balbir, On Sat, Jan 23, 2016 at 07:59:20PM +1100, Balbir Singh wrote: > On Fri, 22 Jan 2016 12:49:02 +0530 > Shilpasri G Bhat wrote: > > > cpu_to_chip_id() does a DT walk through to find out the chip id by > > taking a contended device tree lock. This adds an unnecessary overhead > > in a hot path. So instead of calling cpu_to_chip_id() everytime cache > > the chip ids for all cores in the array 'core_to_chip_map' and use it > > in the hotpath. > > > > Reported-by: Anton Blanchard > > Signed-off-by: Shilpasri G Bhat > > Reviewed-by: Gautham R. Shenoy > > snip > > Does the core_to_chip_map need to be updated/refreshed on/after/ a > cpu (core) hotplug? I presume id's don't change No, the id's don't change on cpu/core hotplug. The core_to_chip_map is initialized in init_chip_info() where we use for_each_possible_cpu(). Thanks for the review! > > Balbir > -- Thanks and Regards gautham.