[CCing the regression list, as it should be in the loop for regressions: https://docs.kernel.org/admin-guide/reporting-regressions.html] [also adding the author of the culprit (Trond) and the second NFS client maintainer (Anna) to the list of recipients] [TLDR: I'm adding this report to the list of tracked Linux kernel regressions; the text you find below is based on a few templates paragraphs you might have encountered already in similar form. See link in footer if these mails annoy you.] On 07.03.23 18:38, Daire Byrne wrote: > I noticed a change in behaviour in the v6.2.x client versus v6.1.12 (and below). > > We have some servers that mount Netapps from different locations many > milliseconds away, and these contain apps and libs that get added to > the LD_LIBRARY_PATH and PATH on remote login. > > I then noticed that when I ssh'd into a remote server that had these > mounts and the shell was starting, the first login was normal and I > observed an expected flurry of lookups,getattrs and access calls for a > grand total of only ~120 packets to the Netapp. > > But when I disconnect and reconnect (ssh), now I see a flood of access > calls to the netapp for a handful of repeating filehandles which look > something like: > > 2700 85.942563180 10.23.112.10 → 10.23.21.11 NFS 254 V3 ACCESS Call, > FH: 0x7f36addc, [Check: RD LU MD XT DL] > 2701 85.999838796 10.23.21.11 → 10.23.112.10 NFS 190 V3 ACCESS Reply > (Call In 2700), [Allowed: RD LU MD XT DL] > 2702 85.999970825 10.23.112.10 → 10.23.21.11 NFS 254 V3 ACCESS Call, > FH: 0x7f36addc, [Check: RD LU MD XT DL] > 2703 86.055340946 10.23.21.11 → 10.23.112.10 NFS 190 V3 ACCESS Reply > (Call In 2702), [Allowed: RD LU MD XT DL] > 2704 86.056865308 10.23.112.10 → 10.23.21.11 NFS 254 V3 ACCESS Call, > FH: 0x7f36addc, [Check: RD LU MD XT DL] > 2705 86.112233415 10.23.21.11 → 10.23.112.10 NFS 190 V3 ACCESS Reply > (Call In 2704), [Allowed: RD LU MD XT DL] > > This time we total 5000+ packets for this login which becomes very > noticeable when the Netapp is 50ms away. > > I didn't understand why the first login was fine but the second goes > into this repeating access pattern. I set actimeo=3600 (long) but it > does not seem to affect it. > > I do not see this prior to v6.2 where repeated logins are equally fast > and we don't see the repeating access calls. > > So a bit of digging through the v6.2 changes and this looked like the > relevant change: > > commit 0eb43812c027 ("NFS: Clear the file access cache upon login”) > [PATCH] NFS: Judge the file access cache's timestamp in rcu path? > > I reverted those and got the prior (v6.1) performance. > > What constitutes a login exactly? I also have services like "sysstat" > or pcp that cause a systemd-logind to trigger regularly on our > machines.... does that count and invalidate the cache? > > Do the repeated access calls on the same handful of filehandles make > sense? Even prior to those patches (or v6.1) there are only a couple > of ACCESS calls to the Netapp on login. > > We are a bit unique in that we run quite a few WAN high latency NFS > workflows so are happy to trade long lived caches (e.g. actimeo and > even nocto on occasion) for lower ops at the expense of total > correctness. Thanks for the report. To be sure the issue doesn't fall through the cracks unnoticed, I'm adding it to regzbot, the Linux kernel regression tracking bot: #regzbot ^introduced 0eb43812c027 #regzbot title nfs: flood of access on second log-in (first is fine) #regzbot ignore-activity This isn't a regression? This issue or a fix for it are already discussed somewhere else? It was fixed already? You want to clarify when the regression started to happen? Or point out I got the title or something else totally wrong? Then just reply and tell me -- ideally while also telling regzbot about it, as explained by the page listed in the footer of this mail. Developers: When fixing the issue, remember to add 'Link:' tags pointing to the report (the parent of this mail). See page linked in footer for details. Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat) -- Everything you wanna know about Linux kernel regression tracking: https://linux-regtracking.leemhuis.info/about/#tldr That page also explains what to do if mails like this annoy you.
