All of lore.kernel.org
 help / color / mirror / Atom feed
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20150422152940.GC3007@worktop.Skamania.guest \
    --to=peterz@infradead.org \
    --cc=eric.dumazet@gmail.com \
    --cc=linaro-kernel@lists.linaro.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@redhat.com \
    --cc=realmz6@gmail.com \
    --cc=shashim@codeaurora.org \
    --cc=tglx@linutronix.de \
    --cc=viresh.kumar@linaro.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.