netdev - Re: [PATCH 1/1] net: Introduce recvmmsg socket syscall

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Message-ID: <20091013015637.GB21809@ghostprotocols.net>
Date:	Mon, 12 Oct 2009 22:56:37 -0300
From:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
To:	Nir Tzachar <nir.tzachar@...il.com>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	Caitlin Bestler <caitlin.bestler@...il.com>,
	Chris Van Hoof <vanhoof@...hat.com>,
	Clark Williams <williams@...hat.com>,
	Neil Horman <nhorman@...driver.com>,
	Nivedita Singhvi <niv@...ibm.com>,
	Paul Moore <paul.moore@...com>,
	Rémi Denis-Courmont 
	<remi.denis-courmont@...ia.com>,
	Steven Whitehouse <steve@...gwyn.com>
Subject: Re: [PATCH 1/1] net: Introduce recvmmsg socket syscall

Em Mon, Oct 12, 2009 at 07:53:43PM +0200, Nir Tzachar escreveu:
> Hi Arnaldo.
> 
> Do you have any plans on how we can further investigate the delays I
> have seen with the second part of the patch? I have tried to simply
> unlock/lock the socket's mutex every couple of iterations inside the

Yeah, that is what tcp does, look at tcp_recvmsg (net/ipv4/tcp.c, line
1505), so I think we should do something along those lines, exactly when
and after which tests is a matter of experimentation.

I'll resume investigation tomorrow.

> loop (to allow the system to process some backlog), but this seems to
> have little to no effect.
 
> Also, a way to enable/disable the no_lock version at runtime will
> greatly help in testing. Maybe by first introducing a second syscall,
> recvmmsg_no_lock, for testing purposes??

I'll come up with a way for that to be possible.

- Arnaldo
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