On Tue, Jul 10, 2012 at 04:52:03PM +0400, Michael Tokarev wrote: > I tried to debug this again, maybe to reproduce in a virtual machine, > and found out that it is only 32bit server code shows this issue: > after updating the kernel on the server to 64bit (the same version) > I can't reproduce this issue anymore. Rebooting back to 32bit, > and voila, it is here again. > > Something apparenlty isn't right on 32bits... ;) > > (And yes, the prob is still present and is very annoying :) OK, that's very useful, thanks. So probably a bug got introduced in the 32-bit case between 2.6.32 and 3.0. My personal upstream testing is normally all x86_64 only. I'll kick off a 32-bit install and see if I can reproduce this quickly. Let me know if you're able to narrow this down any more. --b. > > Thanks, > > /mjt > > > On 31.05.2012 17:51, Michael Tokarev wrote: > > On 31.05.2012 17:46, Myklebust, Trond wrote: > >> On Thu, 2012-05-31 at 17:24 +0400, Michael Tokarev wrote: > > [] > >>> I started tcpdump: > >>> > >>> tcpdump -npvi br0 -s 0 host 192.168.88.4 and \( proto ICMP or port 2049 \) -w nfsdump > >>> > >>> on the client (192.168.88.2). Next I mounted a directory on the client, > >>> and started reading (tar'ing) a directory into /dev/null. It captured a > >>> few stalls. Tcpdump shows number of packets it got, the stalls are at > >>> packet counts 58090, 97069 and 97071. I cancelled the capture after that. > >>> > >>> The resulting file is available at http://www.corpit.ru/mjt/tmp/nfsdump.xz , > >>> it is 220Mb uncompressed and 1.3Mb compressed. The source files are > >>> 10 files of 1Gb each, all made by using `truncate' utility, so does not > >>> take place on disk at all. This also makes it obvious that the issue > >>> does not depend on the speed of disk on the server (since in this case, > >>> the server disk isn't even in use). > >> > >> OK. So from the above file it looks as if the traffic is mainly READ > >> requests. > > > > The issue here happens only with reads. > > > >> In 2 places the server stops responding. In both cases, the client seems > >> to be sending a single TCP frame containing several COMPOUNDS containing > >> READ requests (which should be legal) just prior to the hang. When the > >> server doesn't respond, the client pings it with a RENEW, before it ends > >> up severing the TCP connection and then retransmitting. > > > > And sometimes -- speaking only from the behavour I've seen, not from the > > actual frames sent -- server does not respond to the RENEW too, in which > > case the client reports "nfs server no responding", and on the next > > renew it may actually respond. This happens too, but much more rare. > > > > During these stalls, ie, when there's no network activity at all, > > the server NFSD threads are busy eating all available CPU. > > > > What does it all tell us? :) > > > > Thank you! > > > > /mjt > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > > the body of a message to majordomo@xxxxxxxxxxxxxxx > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > Please read the FAQ at http://www.tux.org/lkml/ > -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
