Date: Fri, 13 May 2011 17:01:54 +0400 From: Maxim Dounin <mdounin@mdounin.ru> To: Michael <michael@gameservice.ru> Cc: freebsd-net@freebsd.org Subject: Re: Random TCP 3 second delay Message-ID: <20110513130154.GV42265@mdounin.ru> In-Reply-To: <1069574542.20110512235022@gameservice.ru> References: <17710363528.20110512130123@gameservice.ru> <20110512104939.GS42265@mdounin.ru> <1069574542.20110512235022@gameservice.ru>
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Hello! On Thu, May 12, 2011 at 11:50:22PM +0300, Michael wrote: > > MD> 3 seconds delay usually indicate packet loss somewhere along the > MD> path. You have to examine your network between nginx and your app > MD> to find out where (and why) packets are lost. > I don't think i have packet loss, traffic is going via loopback Packet loss is quite possible over loopback as well, though it's usually caused by some resource shortage or policy rules in action. BTW, please make sure you don't have net.inet.tcp.nolocaltimewait set. > MD> Some basic steps on FreeBSD include looking though "netstat -id", > MD> "netstat -s" output, "vmstat -z" output and your ethernet > MD> controller stats via "sysctl dev.<driver>" (if any). > I don't see dropped packets on lo0 with netstat -id > What should i see in "netstat -s" and "vmstat -z"? In netstat - look for various drops and overflows, most notably syncache and others tcp-related. In vmstat -z - look for allocation failures and/or full zones, most notably mbufs and other tcp-related zones. > MD> You may also want to check if you by accident have some statefull > MD> firewall between nginx and backend. > I have only ipfw rules, and the first rule is accepting local > traffic: 00005 8211184509 4547370329265 allow ip from me to me > > can this be the problem? AFAIK it shouldn't, but you may want to check sysctl net.inet.ip.fw.dyn_count and net.inet.ip.fw.dyn_max sysctl's anyway. Maxim Dounin
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