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Date: Sat, 23 Jan 2016 19:59:20 +1100
From: Balbir Singh <bsingharora@gmail.com>
To: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>
Cc: 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
Subject: Re: [PATCH v6 2/5] cpufreq: powernv: Remove cpu_to_chip_id() from
 hot-path
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On Fri, 22 Jan 2016 12:49:02 +0530
Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com> 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 <anton@samba.org>
> Signed-off-by: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>
> Reviewed-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>

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

Balbir