netdev - RE: [PATCH v9 net-next 5/7] net: simple poll/select low latency socket poll

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Message-ID: <1370440808.24311.254.camel@edumazet-glaptop>
Date:	Wed, 05 Jun 2013 07:00:08 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Laight <David.Laight@...LAB.COM>
Cc:	Eliezer Tamir <eliezer.tamir@...ux.intel.com>,
	David Miller <davem@...emloft.net>,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	Jesse Brandeburg <jesse.brandeburg@...el.com>,
	Don Skidmore <donald.c.skidmore@...el.com>,
	e1000-devel@...ts.sourceforge.net,
	Willem de Bruijn <willemb@...gle.com>,
	Ben Hutchings <bhutchings@...arflare.com>,
	Andi Kleen <andi@...stfloor.org>, HPA <hpa@...or.com>,
	Eilon Greenstien <eilong@...adcom.com>,
	Or Gerlitz <or.gerlitz@...il.com>,
	Amir Vadai <amirv@...lanox.com>,
	Eliezer Tamir <eliezer@...ir.org.il>
Subject: RE: [PATCH v9 net-next 5/7] net: simple poll/select low latency
 socket poll

On Wed, 2013-06-05 at 14:49 +0100, David Laight wrote:
> > I am a bit uneasy with this one, because an applicatio polling() on one
> > thousand file descriptors using select()/poll(), will call sk_poll_ll()
> > one thousand times.
> 
> Anything calling poll() on 1000 fds probably has performance
> issues already! Which is why kevent schemes have been added.
> 

You'll be surprised but many applications still use poll(),
and not epoll() or whatever OS specific interface, because they
are non portable or buggy. (I played with FreeBSD and kevent crashed
easily at 64,000 fds, while the epoll() version reached 4,000,000 fds
with no problems)




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