linux-kernel - Re: [PATCH 1/2] timer: Avoid waking up an idle-core by migrate running timer

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Date:	Tue, 21 Apr 2015 14:54:55 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	viresh kumar <viresh.kumar@...aro.org>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	linaro-kernel@...ts.linaro.org, linux-kernel@...r.kernel.org,
	Steven Miao <realmz6@...il.com>, shashim@...eaurora.org
Subject: Re: [PATCH 1/2] timer: Avoid waking up an idle-core by migrate
 running timer

On Tue, 2015-04-21 at 23:32 +0200, Thomas Gleixner wrote:

> 
> Are you realizing that __mod_timer() is a massive hotpath for network
> heavy workloads?

BTW I was considering using mod_timer_pinned() from these networking
timers (ie sk_reset_timer())

get_nohz_timer_target() sounds cool for laptop users, but is one cause
for bad responses to DDOS, when the selected cpu gets stressed.

This is the reason I used mod_timer_pinned() in commit 789f558cfb3680ae
("tcp/dccp: get rid of central timewait timer")



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