On Wed, Jan 12, 2022 at 03:56:04PM -0800, Darrick J. Wong wrote: > On Tue, Jan 11, 2022 at 09:58:29AM -0800, Darrick J. Wong wrote: > > On Tue, Jan 11, 2022 at 04:04:37PM +1100, Dave Chinner wrote: > > > On Thu, Jan 06, 2022 at 01:40:33PM -0800, Darrick J. Wong wrote: > > > > On Fri, Dec 10, 2021 at 11:09:56AM +1100, Dave Chinner wrote: > > > > > Hi Darrick, > > > > > > > > > > Can you please pull the following changes from the tag listed below > > > > > for the XFS dev tree? > > > > > > > > Hi Dave, > > > > > > > > I tried, but the regressions with generic/017 persist. It trips the > > > > ticket reservation pretty consistently within 45-60 seconds of starting, > > > > at least on the OCI VM that I created. /dev/sd[ab] are (software > > > > defined) disks that can sustain reads of ~50MB/s and ~5000iops; and > > > > writes of about half those numbers. > > > > > > > > run fstests generic/017 at 2022-01-06 13:18:59 > > > > XFS (sda4): Mounting V5 Filesystem > > > > XFS (sda4): Ending clean mount > > > > XFS (sda4): Quotacheck needed: Please wait. > > > > XFS (sda4): Quotacheck: Done. > > > > XFS (sda4): ctx ticket reservation ran out. Need to up reservation > > > > XFS (sda4): ticket reservation summary: > > > > XFS (sda4): unit res = 548636 bytes > > > > XFS (sda4): current res = -76116 bytes > > > > XFS (sda4): original count = 1 > > > > XFS (sda4): remaining count = 1 > > > > XFS (sda4): Log I/O Error (0x2) detected at xlog_write+0x5ee/0x660 [xfs] (fs/xfs/xfs_log.c:2499). Shutting down filesystem. > > > > XFS (sda4): Please unmount the filesystem and rectify the problem(s) > > > > XFS (sda3): Unmounting Filesystem > > > > XFS (sda4): Unmounting Filesystem > > > > > > Ok, I *think* I've worked out what was going on here. The patch > > > below has run several hundred iterations of g/017 with an external > > > log on two different fs/log size configurations that typically > > > reproduced in within 10 cycles. > > > > > > Essentially, the problem is largely caused by using > > > XLOG_CIL_BLOCKING_SPACE_LIMIT() instead of XLOG_CIL_SPACE_LIMIT() > > > when determining how much used space we can allow the percpu > > > counters to accumulate before aggregating them back into the global > > > counter. Using the hard limit meant that we could accumulate almost > > > the entire hard limit before we aggregate even a single percpu value > > > back into the global limit, resulting in failing to trigger either > > > condition for aggregation until we'd effectively blown through the > > > hard limit. > > > > > > This then meant the extra reservations that need to be taken for > > > space used beyond the hard limit didn't get stolen for the ctx > > > ticket, and it then overruns. > > > > > > It also means that we could overrun the hard limit substantially > > > before throttling kicked in. With the percpu aggregation threshold > > > brought back down to the (soft limit / num online cpus) we are > > > guaranteed to always start aggregation back into the global counter > > > before or at the point in time the soft limit should be hit, meaning > > > that we start updating the global counter much sooner and so are it > > > tracks actual space used once over the soft limit much more closely. > > > > > > Darrick, can you rerun the branch with the patch below also included, and > > > see if it reproduces on your setup? If it does, can you grab a trace > > > of the trace_printk() calls I left in the patch? > > > > Ok, I'll do that and report back. > > ...everything passes now, except for generic/650 on the same machine > that has a 128M external log: > > [21310.267037] run fstests generic/650 at 2022-01-11 22:41:45 > [21311.121539] XFS (sda3): Mounting V5 Filesystem > [21312.295609] XFS (sda3): Ending clean mount > [21314.160622] smpboot: CPU 2 is now offline > [21314.737842] smpboot: Booting Node 0 Processor 2 APIC 0x2 > [21314.740726] kvm-clock: cpu 2, msr 43f608081, secondary cpu clock > [21314.787354] kvm-guest: stealtime: cpu 2, msr 43fd1b040 > [21315.917154] smpboot: CPU 1 is now offline > [21317.993809] x86: Booting SMP configuration: > [21317.996484] smpboot: Booting Node 0 Processor 1 APIC 0x1 > [21318.001940] kvm-clock: cpu 1, msr 43f608041, secondary cpu clock > [21318.020207] kvm-guest: stealtime: cpu 1, msr 43fc9b040 > [21320.126617] smpboot: CPU 3 is now offline > [21320.127744] XFS (sda3): ctx ticket reservation ran out. Need to up reservation > [21320.153944] XFS (sda3): ticket reservation summary: > [21320.158868] XFS (sda3): unit res = 2100 bytes > [21320.163064] XFS (sda3): current res = -40 bytes > [21320.167323] XFS (sda3): original count = 1 > [21320.170436] XFS (sda3): remaining count = 1 > [21320.171742] XFS (sda3): Log I/O Error (0x2) detected at xlog_write+0x5f3/0x670 [xfs] (fs/xfs/xfs_log.c:2512). Shutting down filesystem. > [21320.176445] XFS (sda3): Please unmount the filesystem and rectify the problem(s) > [21320.179719] potentially unexpected fatal signal 6. > [21320.182490] potentially unexpected fatal signal 6. > [21320.182632] potentially unexpected fatal signal 6. > [21320.183842] CPU: 0 PID: 3460987 Comm: fsstress Tainted: G W 5.16.0-rc5-djwx #rc5 79050ab45c4cbd1b9fbe98125ec0eea3a2cdfa1d Different issue. That's a CPU hotplug problem, not a general accounting issue. Hotplug sucks, not sure yet if there's a way to avoid the race that causes this. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx
