linux-kernel - Re: [PATCH] af_unix: unix_write

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Date:	Wed, 24 Nov 2010 00:20:32 +0000
From:	Alban Crequy <alban.crequy@...labora.co.uk>
To:	Pauli Nieminen <pauli.nieminen@...labora.co.uk>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	Davide Libenzi <davidel@...ilserver.org>,
	"David S. Miller" <davem@...emloft.net>,
	Stephen Hemminger <shemminger@...tta.com>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	Alexey Dobriyan <adobriyan@...il.com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Rainer Weikusat <rweikusat@...gmbh.com>
Subject: Re: [PATCH] af_unix: unix_write_space() use keyed wakeups

Le Wed, 24 Nov 2010 01:27:56 +0200,
Pauli Nieminen <pauli.nieminen@...labora.co.uk> a écrit :

> ----- Original message -----
> > Le Sat, 30 Oct 2010 08:44:44 +0200,
> > Eric Dumazet <eric.dumazet@...il.com> a écrit :
> > 
> > > We still loop on 800 items, on each
> > > wake_up_interruptible_sync_poll() call, so maybe we want to
> > > optimize this later, adding a global key, ORing all items keys. I
> > > dont think its worth the added complexity, given the biased usage
> > > of your program (800 'listeners' to one event). Is it a real life
> > > scenario ?
> > 
> > Pauli Nieminen told me about his performance problem in select() so
> > I wrote the test program but I don't know what exactly is the real
> > life scenario.
> > 
> 
> Real world scenario is xsever that has tens client connections to
> manage. When xserver is happily sleeping at seclect call some client
> reading events/replies from server triggers in kernel looping over
> all xserver fds. xserver isn't waiting for socket to became writeable
> in ussual cases so kernel schedules back to client.

But are they SOCK_STREAM or SOCK_DGRAM sockets? The patches fix
performances with SOCK_DGRAM. If the xserver scenario is with
SOCK_STREAM sockets, your problem is probably still unfixed.

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