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

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Date:	Wed, 30 May 2007 13:30:02 +0400
From:	Evgeniy Polyakov <johnpol@....mipt.ru>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Jeff Garzik <jeff@...zik.org>, 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>,
	"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

On Wed, May 30, 2007 at 10:54:00AM +0200, Ingo Molnar (mingo@...e.hu) wrote:
> 
> * Evgeniy Polyakov <johnpol@....mipt.ru> wrote:
> 
> > I did not want to start with another round of ping-pong insults :), 
> > but, Ingo, you did not show that kevent works worse. I did show that 
> > sometimes it works better. It flawed from 0 to 30% win in that tests, 
> > in results Johann Bork presented kevent and epoll behaved the same. In 
> > results I posted earlier, I said, that sometimes epoll behaved better, 
> > sometimes kevent. [...]
> 
> let me refresh your recollection:
> 
>   http://lkml.org/lkml/2007/2/25/116
> 
> where you said:
> 
>  "But note, that on my athlon64 3500 test machine kevent is about 7900
>   requests per second compared to 4000+ epoll, so expect a challenge."

You can also find in that threads that I managed to run epoll server on 
that machine with 9k requests per second, although that was not
reproducible again.

> for a long time you made much fuss about how kevents is so much better 
> and how epoll cannot perform and scale as well (you said various 
> arguments why that is supposedly so), and some people bought into the 
> performance argument and advocated kevent due to its supposed 
> performance and scalability advantages - while now we are down to "epoll 
> and kevent are break-even"?

You just draw a picture you want to see.

Even on the kevent page I have links to other people's benchmarks, which
show how kevent behave compared to epoll in theirs load.
_My_ tests showed kevent performance win, you tuned my (can be
broken) epoll code and results changed - this is developemnt process,
where things are not obtained from the air.

> in my book that is way too much of a difference, it is (best-case) a way 
> too sloppy approach to something as fundamental as Linux's basic event 
> model and design, and it is also compounded by your continued "nothing 
> happened, really, lets move on" stance. Losing trust is easy, winning it 
> back is hard. Let me reuse a phrase of yours: "expect a challenge".

Well, I do not care much about what people think I did wrong or right.
There are obviously bad and good ideas and implementations.
I might be absolutely wrong with something, but that is a process of
solving problems, which I really enjoy.

I just want that there sould be no personal insults, if I made such things,
shame on me :)

> 	Ingo

-- 
	Evgeniy Polyakov
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