This sounds a bit like my bugzilla ticket: https://bugzilla.kernel.org/show_bug.cgi?id=213887 But in my case the client rarely recovers from the timeout so the hang becomes permanent. My setup is a bit more complicated though (NFS re-exporting). Daire On Tue, 10 Aug 2021 at 02:29, NeilBrown <neilb@xxxxxxx> wrote: > > On Tue, 10 Aug 2021, Mike Javorski wrote: > > Managed to get the rpcdebug info for some freezes today. I had a loop > > running to call the rpcbind command that Neil provided and then sleep > > for 2 seconds. Each triggering event was the opening of a new video > > file (I was shuffling through files with mpv). I haven't managed to > > get a tcp capture yet trying to get one that isn't too massive, but > > the timing is tricky, and this doesn't happen every time. > > > > Thanks for the logs. > > They show consistent "a:call_status" and "q:xprt_pending". They also > show a timeout in the range 10000-20000. This number is in 'jiffies', > which is normally millisecs, so 10 to 20 seconds. > > That means the RPC layer (thinks it has) sent a request (made a call) > and is waiting for a reply to arrive over the network transport (i.e. > the TCP connection). However that would typically involve a much longer > timeout. For NFSv3 and 4.0, 60 seconds is the norm. For NFSv4.1 I > *think* there is no timeout as NFS never resends requests unless the TCP > connection is broken. So I don't know what to make of that. > > Given the fact that it recovers in 5-10 seconds, it seems very likely > that it actually has sent the request (presumably the timeout doesn't > expire). Mostly likely the server is being delayed in replying. A > tcpdump trace would confirm this. > > I don't think you've said anything about what NFS server you are using. > It is Linux, or something else? If Linux, what kernel do you run there? > > One thing that might cause a delay when accessing a file is if some > other client has a 'delegation' and takes a while to return it. > e.g. > client2 creates a file for writing > server gives it a 'write delegation' > client2 queues up lots of write request > client1 asks to read the file. > server says to client2 "please return the delegation" > client2 starts flushing its data, but either takes too long or > has some other hiccup. Eventually it is returned, or the server > revokes it > server tells clients one it can read now. > > This is leading to me asking: do you have other NFS clients that might > be accessing the same file, or might have accessed it recently? > > NeilBrown > > > > ----------------------------- > > > > [31229.965368] -pid- flgs status -client- --rqstp- -timeout ---ops-- > > [31229.965370] 44224 c801 0 8c478d70 2473aa3b 15395 8531859 > > nfsv4 READ a:call_status [sunrpc] q:xprt_pending > > [31229.965411] 44225 c801 0 8c478d70 a7d3b9b8 15395 8531859 > > nfsv4 READ a:call_status [sunrpc] q:xprt_pending > > [31231.966982] -pid- flgs status -client- --rqstp- -timeout ---ops-- > > [31231.966986] 44224 c801 0 8c478d70 2473aa3b 14795 8531859 > > nfsv4 READ a:call_status [sunrpc] q:xprt_pending > > [31231.967027] 44225 c801 0 8c478d70 a7d3b9b8 14795 8531859 > > nfsv4 READ a:call_status [sunrpc] q:xprt_pending > > [31233.968741] -pid- flgs status -client- --rqstp- -timeout ---ops-- > > [31233.968745] 44224 c801 0 8c478d70 2473aa3b 14194 8531859 > > nfsv4 READ a:call_status [sunrpc] q:xprt_pending > > [31233.968787] 44225 c801 0 8c478d70 a7d3b9b8 14194 8531859 > > nfsv4 READ a:call_status [sunrpc] q:xprt_pending > > > > ----------------------------- > > > > [31292.534529] -pid- flgs status -client- --rqstp- -timeout ---ops-- > > [31292.534530] 45744 c801 0 8c478d70 2473aa3b 15340 8531859 > > nfsv4 READ a:call_status [sunrpc] q:xprt_pending > > [31292.534554] 45745 c801 0 8c478d70 50cbef7b 15342 8531859 > > nfsv4 READ a:call_status [sunrpc] q:xprt_pending > > [31294.536203] -pid- flgs status -client- --rqstp- -timeout ---ops-- > > [31294.536206] 45744 c801 0 8c478d70 2473aa3b 14740 8531859 > > nfsv4 READ a:call_status [sunrpc] q:xprt_pending > > [31294.536232] 45745 c801 0 8c478d70 50cbef7b 14742 8531859 > > nfsv4 READ a:call_status [sunrpc] q:xprt_pending > > [31296.537826] -pid- flgs status -client- --rqstp- -timeout ---ops-- > > [31296.537830] 45744 c801 0 8c478d70 2473aa3b 14139 8531859 > > nfsv4 READ a:call_status [sunrpc] q:xprt_pending > > [31296.537871] 45745 c801 0 8c478d70 50cbef7b 14141 8531859 > > nfsv4 READ a:call_status [sunrpc] q:xprt_pending > > [31298.539474] -pid- flgs status -client- --rqstp- -timeout ---ops-- > > [31298.539478] 45744 c801 0 8c478d70 2473aa3b 13539 8531859 > > nfsv4 READ a:call_status [sunrpc] q:xprt_pending > > [31298.539522] 45745 c801 0 8c478d70 50cbef7b 13541 8531859 > > nfsv4 READ a:call_status [sunrpc] q:xprt_pending > > [31300.541040] -pid- flgs status -client- --rqstp- -timeout ---ops-- > > [31300.541044] 46048 c801 0 8c478d70 50cbef7b 17965 8531859 > > nfsv4 READ a:call_status [sunrpc] q:xprt_pending > > [31300.541108] 46049 c801 0 8c478d70 2473aa3b 17965 8531859 > > nfsv4 READ a:call_status [sunrpc] q:xprt_pending > > [31302.542632] -pid- flgs status -client- --rqstp- -timeout ---ops-- > > [31302.542635] 46922 c801 0 8c478d70 50cbef7b 18000 8531859 > > nfsv4 READ a:call_status [sunrpc] q:xprt_pending > > > > --------------------------- > > > > [31375.046020] -pid- flgs status -client- --rqstp- -timeout ---ops-- > > [31375.046022] 47336 c801 0 8c478d70 cebaa9a6 15964 8531859 > > nfsv4 READ a:call_status [sunrpc] q:xprt_pending > > [31375.046048] 47337 c801 0 8c478d70 f7145d4d 15964 8531859 > > nfsv4 READ a:call_status [sunrpc] q:xprt_pending > > [31377.047361] -pid- flgs status -client- --rqstp- -timeout ---ops-- > > [31377.047365] 47336 c801 0 8c478d70 cebaa9a6 15364 8531859 > > nfsv4 READ a:call_status [sunrpc] q:xprt_pending > > [31377.047406] 47337 c801 0 8c478d70 f7145d4d 15364 8531859 > > nfsv4 READ a:call_status [sunrpc] q:xprt_pending > > [31379.048801] -pid- flgs status -client- --rqstp- -timeout ---ops-- > > [31379.048805] 47336 c801 0 8c478d70 cebaa9a6 14764 8531859 > > nfsv4 READ a:call_status [sunrpc] q:xprt_pending > > [31379.048845] 47337 c801 0 8c478d70 f7145d4d 14764 8531859 > > nfsv4 READ a:call_status [sunrpc] q:xprt_pending > > [31381.050376] -pid- flgs status -client- --rqstp- -timeout ---ops-- > > [31381.050380] 47336 c801 0 8c478d70 cebaa9a6 14163 8531859 > > nfsv4 READ a:call_status [sunrpc] q:xprt_pending > > [31381.050421] 47337 c801 0 8c478d70 f7145d4d 14163 8531859 > > nfsv4 READ a:call_status [sunrpc] q:xprt_pending > > [31383.051746] -pid- flgs status -client- --rqstp- -timeout ---ops-- > > [31383.051749] 47336 c801 0 8c478d70 cebaa9a6 13563 8531859 > > nfsv4 READ a:call_status [sunrpc] q:xprt_pending > > [31383.051775] 47337 c801 0 8c478d70 f7145d4d 13563 8531859 > > nfsv4 READ a:call_status [sunrpc] q:xprt_pending > > [31385.053182] -pid- flgs status -client- --rqstp- -timeout ---ops-- > > [31385.053185] 47342 c801 0 8c478d70 f7145d4d 17980 8531859 > > nfsv4 READ a:call_status [sunrpc] q:xprt_pending > > [31387.054422] -pid- flgs status -client- --rqstp- -timeout ---ops-- > > [31387.054426] 47818 c801 0 8c478d70 f7145d4d 17761 8531859 > > nfsv4 READ a:call_status [sunrpc] q:xprt_pending > > [31387.054467] 47819 c801 0 8c478d70 cebaa9a6 17762 8531859 > > nfsv4 READ a:call_status [sunrpc] q:xprt_pending > > > > > > - mike > > > > > > On Sun, Aug 8, 2021 at 5:28 PM Mike Javorski <mike.javorski@xxxxxxxxx> wrote: > > > > > > Appreciate the insights Neil. I will make an attempt to > > > trigger/capture the fault if I can. > > > > > > - mike > > > > > > On Sun, Aug 8, 2021 at 5:01 PM NeilBrown <neilb@xxxxxxx> wrote: > > > > > > > > On Mon, 09 Aug 2021, Mike Javorski wrote: > > > > > I have been experiencing nfs file access hangs with multiple release > > > > > versions of the 5.13.x linux kernel. In each case, all file transfers > > > > > freeze for 5-10 seconds and then resume. This seems worse when reading > > > > > through many files sequentially. > > > > > > > > A particularly useful debugging tool for NFS freezes is to run > > > > > > > > rpcdebug -m rpc -c all > > > > > > > > while the system appears frozen. As you only have a 5-10 second window > > > > this might be tricky. > > > > Setting or clearing debug flags in the rpc module (whether they are > > > > already set or not) has a side effect if listing all RPC "tasks" which a > > > > waiting for a reply. Seeing that task list can often be useful. > > > > > > > > The task list appears in "dmesg" output. If there are not tasks > > > > waiting, nothing will be written which might lead you to think it didn't > > > > work. > > > > > > > > As Chuck hinted, tcpdump is invaluable for this sort of problem. > > > > tcpdump -s 0 -w /tmp/somefile.pcap port 2049 > > > > > > > > will capture NFS traffic. If this can start before a hang, and finish > > > > after, it may contain useful information. Doing that in a way that > > > > doesn't create an enormous file might be a challenge. It would help if > > > > you found a way trigger the problem. Take note of the circumstances > > > > when it seems to happen the most. If you can only produce a large file, > > > > we can probably still work with it. > > > > tshark -r /tmp/somefile.pcap > > > > will report the capture one line per packet. You can look for the > > > > appropriate timestamp, note the frame numbers, and use "editcap" > > > > to extract a suitable range of packets. > > > > > > > > NeilBrown > > > > > > > > > > > > > > > > > > My server: > > > > > - Archlinux w/ a distribution provided kernel package > > > > > - filesystems exported with "rw,sync,no_subtree_check,insecure" options > > > > > > > > > > Client: > > > > > - Archlinux w/ latest distribution provided kernel (5.13.9-arch1-1 at writing) > > > > > - nfs mounted via /net autofs with "soft,nodev,nosuid" options > > > > > (ver=4.2 is indicated in mount) > > > > > > > > > > I have tried the 5.13.x kernel several times since the first arch > > > > > release (most recently with 5.13.9-arch1-1), all with similar results. > > > > > Each time, I am forced to downgrade the linux package to a 5.12.x > > > > > kernel (5.12.15-arch1 as of writing) to clear up the transfer issues > > > > > and stabilize performance. No other changes are made between tests. I > > > > > have confirmed the freezing behavior using both ext4 and btrfs > > > > > filesystems exported from this server. > > > > > > > > > > At this point I would appreciate some guidance in what to provide in > > > > > order to diagnose and resolve this issue. I don't have a lot of kernel > > > > > debugging experience, so instruction would be helpful. > > > > > > > > > > - mike > > > > > > > > > > > > > >
