linux-kernel - Re: [ltt-dev] [RFC PATCH] Poll : add poll_wait_set_exclusive (fixing thundering herd problem in LTTng)

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Message-ID: <20081124121659.GA18987@Krystal>
Date:	Mon, 24 Nov 2008 07:16:59 -0500
From:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	ltt-dev@...ts.casi.polymtl.ca, Ingo Molnar <mingo@...e.hu>,
	linux-kernel@...r.kernel.org,
	William Lee Irwin III <wli@...omorphy.com>
Subject: Re: [ltt-dev] [RFC PATCH] Poll : add poll_wait_set_exclusive
	(fixing thundering herd problem in LTTng)

* KOSAKI Motohiro (kosaki.motohiro@...fujitsu.com) wrote:
> > > I fully agreed this feature is needed.
> > > Actually, I've made similar patch at one years ago.
> > > 
> > > http://marc.info/?l=linux-kernel&m=120257050719087&w=2
> > > 
> > > 
> > > but, I have one question.
> > > My version have epoll support, but yours donesn't have.
> > > Is it intensionally?
> > > 
> > > this is just dumb question, it doesn't mean any objection.
> > 
> > Hrm, actually, your patch seems cleaner than mine, but it adds a branch
> > in the standard hotpath, which mine does not do (but I am not sure it is
> > such an important optimization...). 
> 
> Why do you think poll_wait() is hotpath?
> I think sysm_poll() isn't hotpath because it often cause task sleeping.
> 
> 
> > Is there any reason why your patch
> > did not get merged ?
> 
> my patch was developed for a part of mem_notify patch series.
> but the mem_notify was naked by akpm.
> therefore it lost merging motivation ;-)
> 
> Ingo, I'll rebase and post my patch for -tip tommorow.
> Could you please review it?
> 
> 
> > The only reason I did not make a epoll version is simply because LTTng
> > currently does not support it. :)
> 
> thanks.
> I understand your original intension.
> 

Great, please CC me on this one so I can integrate it to the LTTng tree.

Mathieu


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Mathieu Desnoyers
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