linux-kernel - Re: Syslets, Threadlets, generic AIO support, v6

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Message-ID: <465D43A0.8040307@garzik.org>
Date:	Wed, 30 May 2007 05:28:00 -0400
From:	Jeff Garzik <jeff@...zik.org>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Zach Brown <zach.brown@...cle.com>, linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Christoph Hellwig <hch@...radead.org>,
	Andrew Morton <akpm@....com.au>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Ulrich Drepper <drepper@...hat.com>,
	Evgeniy Polyakov <johnpol@....mipt.ru>,
	"David S. Miller" <davem@...emloft.net>,
	Suparna Bhattacharya <suparna@...ibm.com>,
	Davide Libenzi <davidel@...ilserver.org>,
	Jens Axboe <jens.axboe@...cle.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: Syslets, Threadlets, generic AIO support, v6

Ingo Molnar wrote:
> * Jeff Garzik <jeff@...zik.org> wrote:
> 
>> You should pick up the kevent work :)
> 
> 3 months ago i verified the published kevent vs. epoll benchmark and 
> found that benchmark to be fatally flawed. When i redid it properly 
> kevent showed no significant advantage over epoll. Note that i did those 
> measurements _before_ the recent round of epoll speedups. So unless 
> someone does believable benchmarks i consider kevent an over-hyped, 
> mis-benchmarked complication to do something that epoll is perfectly 
> capable of doing.

You snipped the key part of my response, so I'll say it again:

Event rings (a) most closely match what is going on in the hardware and 
(b) often closely match what is going on in multi-socket, event-driven 
software application.

To echo Uli and paraphrase an ad, "it's the interface, silly."

This is not something epoll is capable of doing, at the present time.

	Jeff


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