linux-kernel - Re: [PATCH] cpu_pm: replace raw_notifier to atomic

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Message-ID: <2bf3cdfa-f8b6-9d32-b3b5-33900cb9122a@linaro.org>
Date:   Sat, 8 Jul 2017 15:25:14 +0800
From:   Alex Shi <alex.shi@...aro.org>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     open list <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Anders Roxell <anders.roxell@...aro.org>,
        Rik van Riel <riel@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        linux-rt-users <linux-rt-users@...r.kernel.org>
Subject: Re: [PATCH] cpu_pm: replace raw_notifier to atomic_notifier



On 07/07/2017 06:25 PM, Sebastian Andrzej Siewior wrote:
> On 2017-07-06 16:47:46 [+0800], Alex Shi wrote:
>> This patch replace a rwlock and raw notifier by atomic notifier which
> + is 
>> protected by spin_lock and rcu.
> …
>> Sebastian suggested using atomic_notifier instead of rwlock, which is not
>> only removing the sleeping in idle, but also getting better latency
>> improvement.
> 
> Did you measure this / have numbers or did you write this because this
> is what RCU does in general?

Uh, I have no number on the performance. The benefit is in the theory.
https://lwn.net/Articles/263130/
But above article give some comparison data of rwlock and RCU.

> 
> Acked-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> 

Thanks a lot!

Regards
Alex