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From: Peter Zijlstra <peterz@infradead.org>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	viresh kumar <viresh.kumar@linaro.org>,
	Ingo Molnar <mingo@redhat.com>,
	linaro-kernel@lists.linaro.org, linux-kernel@vger.kernel.org,
	Steven Miao <realmz6@gmail.com>,
	shashim@codeaurora.org
Subject: Re: [PATCH 1/2] timer: Avoid waking up an idle-core by migrate running timer
Date: Wed, 22 Apr 2015 17:29:40 +0200	[thread overview]
Message-ID: <20150422152940.GC3007@worktop.Skamania.guest> (raw)
In-Reply-To: <1429653295.18561.16.camel@edumazet-glaptop2.roam.corp.google.com>

On Tue, Apr 21, 2015 at 02:54:55PM -0700, Eric Dumazet wrote:
> 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")

Hmm, that sounds unfortunate, this would wreck life for the power aware
laptop/tablet etc.. people.

There is already a sysctl to manage this, is that not enough to mitigate
this problem on the server side of things?

  reply	other threads:[~2015-04-22 15:29 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-31  6:55 [PATCH 0/2] timer: Migrate running timers Viresh Kumar
2015-03-31  6:55 ` [PATCH 1/2] timer: Avoid waking up an idle-core by migrate running timer Viresh Kumar
2015-03-31 14:53   ` Peter Zijlstra
2015-04-14 23:13   ` Thomas Gleixner
2015-04-17  8:12     ` viresh kumar
2015-04-17  8:32       ` Ingo Molnar
2015-04-21 21:32       ` Thomas Gleixner
2015-04-21 21:54         ` Eric Dumazet
2015-04-22 15:29           ` Peter Zijlstra [this message]
2015-04-22 16:02             ` Eric Dumazet
2015-04-22 18:56               ` Thomas Gleixner
2015-04-22 19:59                 ` Eric Dumazet
2015-04-22 21:56                   ` Thomas Gleixner
2015-04-23  6:57                     ` Eric Dumazet
2015-04-23 12:45                       ` Thomas Gleixner
2015-04-25 18:37                         ` Eric Dumazet
2015-05-05 13:00                           ` Thomas Gleixner
2015-05-06 16:33                             ` Eric Dumazet
2015-04-15 15:54   ` Thomas Gleixner
2015-03-31  6:55 ` [PATCH 2/2] timer: Replace base-> 'running_timer' with 'busy' Viresh Kumar
2015-03-31 15:01 ` [PATCH 0/2] timer: Migrate running timers Viresh Kumar

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