From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Scott M. Ferris" Subject: Re: TSO prevents cwnd growth on 2.6 kernels Date: Fri, 25 Mar 2005 13:34:59 -0600 Message-ID: <20050325193458.GA15645@visi.com> References: <20050325181804.GA11633@visi.com> <20050325104000.713229be.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "Scott M. Ferris" , netdev@oss.sgi.com To: "David S. Miller" Content-Disposition: inline In-Reply-To: <20050325104000.713229be.davem@davemloft.net> Sender: netdev-bounce@oss.sgi.com Errors-to: netdev-bounce@oss.sgi.com List-Id: netdev.vger.kernel.org On Fri, Mar 25, 2005 at 10:40:00AM -0800, David S. Miller wrote: > > We know it's busted. I haven't gotten to fixing this stuff > up yet. Perhaps TSO should default to off for all drivers then? I hadn't even noticed it was enabled until after I was debugging the problem. > Are you suggesting to let it go past tp->snd_cwnd? We can't > ever do that. tp->snd_cwnd is a hard limit on the number > of frames we may have outstanding on the network at one time, > TSO or not. No, I think we all agree that exceeding cwnd is a bad idea. I'm just saying that failing to reach cwnd is also broken, especially if it results in tcp_write_xmit() sending nothing at all when cwnd is small. -- Scott M. Ferris, sferris@acm.org