Date: Sun, 17 Jun 2007 13:02:38 -0600 (MDT) From: "M. Warner Losh" <imp@bsdimp.com> To: joe@joeholden.co.uk Cc: net@freebsd.org Subject: Re: Issue with huge numbers of connections Message-ID: <20070617.130238.-1435629453.imp@bsdimp.com> In-Reply-To: <46757818.5030005@joeholden.co.uk> References: <20070617.114133.778151882.imp@bsdimp.com> <46757818.5030005@joeholden.co.uk>
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In message: <46757818.5030005@joeholden.co.uk> Joe Holden <joe@joeholden.co.uk> writes: : M. Warner Losh wrote: : > Greetings, : > : > I have a friend who is having problems with a service he's running. : > He gets billions and billions of connections to this service a day. : > Somewhere between 10^8 and 10^9 connections, he notices that his : > servers lose the ability to accept new connections. These are TCP : > connections. : > : > This is with FreeBSD 6.1R. My first question is: does anybody know if : > the fixes to -current/7.0 have fixed this? Is there a fix that can be : > back ported? He's currently working around the problem by having a : > number of different machines that reboot in a round robin fashion, but : > would like a better solution. : > : > Warner : > _______________________________________________ : Warner, if he hasn't done so already, have you suggested tweaking the : sysctl variables, such as: : kern.maxfilesperproc : kern.ipc.nmbclusters : kern.maxprocperuid : kern.maxfiles : kern.ipc.somaxconn : kern.maxvnodes : : Tweaking those may help, or he may just be exhausting available : resources, IIRC its limited to 65k connections per interface, someone : correct me if I am wrong. Here's the bug report I got: There is still a vague problem with the FreeBSD network interface -- especially the part that handles TCP. Something strange happens after about a week or so (after handling about 10^8 or 10^9 connections). The system becomes unreachable for TCP connections. I have fixed this problem by having all of the FreeBSD systems reboot automatically once a week using a cron job. I have not been able to isolate this issue, but I suspect that there is some kind of problem with the error handling and some resource gets depleted slowly. I realize that this is pretty vague, but I have not been able to find out what actually happens in this case. I believe that each connection lasts on the order of tens or hundreds milliseconds, given what I know about the systems in place. My earlier rephrase omitted a few key points. I suggested that he try to use a newer version of FreeBSD, but since these are a production system, he's hesitant to mess with them... Doing the math on 10^9 connections in a week translates to ~1650/s, so we'd expect there are on the order of 100-200 connections steady state at any time. I suspect that the peak load may be up to 100 times that, which is still only 20000 connections. The hangs don't seem to hang at a peak, but randomly. Given all that, I'm not sure which of the above to try. Warner
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