From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Drake Subject: Re: 2.6.17 regression: Very slow net transfer from some hosts Date: Wed, 12 Apr 2006 01:06:09 +0100 Message-ID: <443C4471.7040407@gentoo.org> References: <443C03E6.7080202@gentoo.org> <443C024C.2070107@psc.edu> <443C0B74.50305@gentoo.org> <443C09A7.2040900@psc.edu> <443C1738.20605@gentoo.org> <443C178B.3030805@psc.edu> <443C2BBA.5010804@gentoo.org> <20060411153315.4132b477@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: John Heffner , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Return-path: To: Stephen Hemminger In-Reply-To: <20060411153315.4132b477@localhost.localdomain> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org Stephen Hemminger wrote: >> This is very familiar, and I just found the article I was thinking of: >> http://lwn.net/Articles/92727/ >> >> I was also hit by that bug, on the same collection of websites, but that >> particular problem was fixed for 2.6.8 or so. So I guess it is extremely >> likely that my ISP has broken routers. nmap isn't able to identify the >> OS of any ISP routers in my path. > > We never fixed it, its kind of hard to fix other peoples equipment ;-) Weird, things started working for me around 2.6.9 without having to modify any sysctl stuff. > Turn off TCP window scaling, your performance will be limited but about > as good as you can get with a corrupting firewall in between. I was wrong in my previous mail where I said that the rmem/wmem output hasn't changed over the two kernels - it has, the 3rd column differs. I simply set those values back to what they were on 2.6.16 and now things work again - I presumably have window scale 2 (scale factor 4) again, which appears to be a decent compromise between having a window and things actually working. For anyone else interested, the ISP is NTL (UK). The fix: echo "4096 16384 131072 " > /proc/sys/net/ipv4/tcp_wmem echo "4096 87380 174760 " > /proc/sys/net/ipv4/tcp_rmem This issue is visible on my 1GB system but not on my laptop (256mb RAM). The key thing is that more memory means a higher window scale factor is used, which appears to trigger ntl's brokenness. Daniel