netdev - Re: [RFC PATCH] [TCP]: Fix lost_retrans loop vs fastpath problems

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Message-ID: <Pine.LNX.4.64.0710111300280.23026@kivilampi-30.cs.helsinki.fi>
Date:	Thu, 11 Oct 2007 13:12:49 +0300 (EEST)
From:	"Ilpo Järvinen" <ilpo.jarvinen@...sinki.fi>
To:	TAKANO Ryousei <takano@...-inc.co.jp>
cc:	Netdev <netdev@...r.kernel.org>,
	David Miller <davem@...emloft.net>,
	Stephen Hemminger <shemminger@...ux-foundation.org>
Subject: Re: [RFC PATCH] [TCP]: Fix lost_retrans loop vs fastpath problems

On Thu, 11 Oct 2007, TAKANO Ryousei wrote:

> From: "Ilpo Järvinen" <ilpo.jarvinen@...sinki.fi>
> Subject: [RFC PATCH] [TCP]: Fix lost_retrans loop vs fastpath problems
> Date: Tue,  9 Oct 2007 15:20:01 +0300
> 
> Thanks Ilpo!  I am trying to evaluate this patch.

There's a minor problem in this 2nd patch, it's just preventing the 
cnt == tp->retrans_out short-circuit from working, not a correctness 
problem though it could affect the performance. I'll post larger patch 
series among which is a fixed version (hopefully today).

> But, I got 
> a kernel panic at net_rx_action() in our experimental setting.
> I am using the net-2.6.24 kernel _without_ this patch. 
> (I will post a bug report separately).

...Please do. :-)

> Anyway, I will report the result as soon as possible.

Thanks. ...It's very interesting to see because it's not that clear
cut how the extra processing that is necessary affects high-speed 
performance, it could add yet another source of RTOs due
processing latency.

-- 
 i.