From: Jamie Lokier <jamie@shareable.org>
To: David Schwartz <davids@webmaster.com>
Cc: Davide Libenzi <davidel@xmailserver.org>,
Eric Varsanyi <e0206@foo21.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [Patch][RFC] epoll and half closed TCP connections
Date: Sun, 13 Jul 2003 22:10:45 +0100 [thread overview]
Message-ID: <20030713211045.GD21612@mail.jlokier.co.uk> (raw)
In-Reply-To: <MDEHLPKNGKAHNMBLJOLKIEEPEFAA.davids@webmaster.com>
David Schwartz wrote:
> For most real-world loads, M is some fraction of N. The fraction
> asymptotically approaches 1 as load increases because under load it takes
> you longer to get back to polling, so a higher fraction of the descriptors
> will be ready when you do.
Ah, but as the fraction approaches 1, you'll find that you are
asymptotically approaching the point where you can't handle the load
_regardless_ of epoll overhead.
> By the way, I'm not arguing against epoll. I believe it will use less
> resources than poll in pretty much every conceivable situation. I simply
> take issue with the argument that it has better ultimate scalability or
> scales at a different order.
It scales according to the amount of work pending, which means that it
doesn't take any _more_ time than actually doing the pending work.
(This assumes you use epoll appropriately; there are many ways to use
epoll which don't have this property).
That was always the complaint about select() and poll(): they dominate
the run time for large numbers of connections. epoll, on the other
hand, will always be in the noise relative to other work.
If you want a formula for slides :), time_polling/time_working is O(1)
with epoll, but O(N) with poll() & select().
-- Jamie
next prev parent reply other threads:[~2003-07-13 20:56 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-07-12 18:16 [Patch][RFC] epoll and half closed TCP connections Eric Varsanyi
2003-07-12 19:44 ` Jamie Lokier
2003-07-12 20:51 ` Eric Varsanyi
2003-07-12 20:48 ` Davide Libenzi
2003-07-12 21:19 ` Eric Varsanyi
2003-07-12 21:20 ` Davide Libenzi
2003-07-12 21:41 ` Davide Libenzi
2003-07-12 23:11 ` Eric Varsanyi
2003-07-12 23:55 ` Davide Libenzi
2003-07-13 1:05 ` Eric Varsanyi
2003-07-13 20:32 ` David Schwartz
2003-07-13 21:10 ` Jamie Lokier [this message]
2003-07-13 23:05 ` David Schwartz
2003-07-13 23:09 ` Davide Libenzi
2003-07-14 8:14 ` Alan Cox
2003-07-14 15:03 ` Davide Libenzi
2003-07-14 1:27 ` Jamie Lokier
2003-07-13 21:14 ` Davide Libenzi
2003-07-13 23:05 ` David Schwartz
2003-07-13 23:11 ` Davide Libenzi
2003-07-13 23:52 ` Entrope
2003-07-14 6:14 ` David Schwartz
2003-07-14 7:20 ` Jamie Lokier
2003-07-14 1:51 ` Jamie Lokier
2003-07-14 6:14 ` David Schwartz
2003-07-15 20:27 ` James Antill
2003-07-16 1:46 ` David Schwartz
2003-07-16 2:09 ` James Antill
2003-07-13 13:12 ` Jamie Lokier
2003-07-13 16:55 ` Davide Libenzi
2003-07-12 20:01 ` Davide Libenzi
2003-07-13 5:24 ` David S. Miller
2003-07-13 14:07 ` Jamie Lokier
2003-07-13 17:00 ` Davide Libenzi
2003-07-13 19:15 ` Jamie Lokier
2003-07-13 23:03 ` Davide Libenzi
2003-07-14 1:41 ` Jamie Lokier
2003-07-14 2:24 ` POLLRDONCE optimisation for epoll users (was: epoll and half closed TCP connections) Jamie Lokier
2003-07-14 2:37 ` Davide Libenzi
2003-07-14 2:43 ` Davide Libenzi
2003-07-14 2:56 ` Jamie Lokier
2003-07-14 3:02 ` Davide Libenzi
2003-07-14 3:16 ` Jamie Lokier
2003-07-14 3:21 ` Davide Libenzi
2003-07-14 3:42 ` Jamie Lokier
2003-07-14 4:00 ` Davide Libenzi
2003-07-14 5:51 ` Jamie Lokier
2003-07-14 6:24 ` Davide Libenzi
2003-07-14 6:57 ` Jamie Lokier
2003-07-14 3:12 ` Jamie Lokier
2003-07-14 3:17 ` Davide Libenzi
2003-07-14 3:35 ` Jamie Lokier
2003-07-14 3:04 ` Jamie Lokier
2003-07-14 3:12 ` Davide Libenzi
2003-07-14 3:27 ` Jamie Lokier
2003-07-14 17:09 ` [Patch][RFC] epoll and half closed TCP connections kuznet
2003-07-14 17:09 ` Davide Libenzi
2003-07-14 21:45 ` Jamie Lokier
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