From: Gautham R Shenoy <ego@linux.vnet.ibm.com>
To: Balbir Singh <bsingharora@gmail.com>
Cc: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>,
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
Date: Mon, 25 Jan 2016 11:08:05 +0530 [thread overview]
Message-ID: <20160125053804.GA5599@in.ibm.com> (raw)
In-Reply-To: <20160123195920.552990ed@cotter.ozlabs.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 <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
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.
next prev parent reply other threads:[~2016-01-25 5:38 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-22 7:19 [PATCH v6 0/5] cpufreq: powernv: Redesign the presentation of throttle notification and solve bug-fixes in the driver Shilpasri G Bhat
2016-01-22 7:19 ` [PATCH v6 1/5] cpufreq: powernv: Hot-plug safe the kworker thread Shilpasri G Bhat
2016-01-25 5:49 ` Viresh Kumar
2016-01-22 7:19 ` [PATCH v6 2/5] cpufreq: powernv: Remove cpu_to_chip_id() from hot-path Shilpasri G Bhat
2016-01-23 8:59 ` Balbir Singh
2016-01-25 5:38 ` Gautham R Shenoy [this message]
2016-01-25 5:53 ` Viresh Kumar
2016-01-22 7:19 ` [PATCH v6 3/5] cpufreq: powernv/tracing: Add powernv_throttle tracepoint Shilpasri G Bhat
2016-01-22 7:19 ` [PATCH v6 4/5] cpufreq: powernv: Replace pr_info with trace print for throttle event Shilpasri G Bhat
2016-01-25 5:58 ` Viresh Kumar
2016-01-22 7:19 ` [PATCH v6 5/5] cpufreq: powernv: Add sysfs attributes to show throttle stats Shilpasri G Bhat
2016-01-23 8:40 ` Balbir Singh
2016-01-25 6:46 ` Shilpasri G Bhat
2016-01-25 5:43 ` [v6, " Michael Ellerman
2016-01-25 5:43 ` Michael Ellerman
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