Date: Fri, 2 Apr 2021 22:50:15 +0200 From: Mathieu Chouquet-Stringer <me+freebsd@mathieu.digital> To: Dave Cottlehuber <dch@skunkwerks.at> Cc: freebsd-fs <freebsd-fs@freebsd.org>, freebsd-current <freebsd-current@freebsd.org>, bryanv@freebsd.org Subject: Re: Scrub incredibly slow with 13.0-RC3 (as well as RC1 & 2) Message-ID: <YGeDh7i/Iu2p6I2o@weirdfishes> In-Reply-To: <3c00c109-ed5a-496c-9339-22b3dc31747a@www.fastmail.com> References: <YFhuxr0qRzchA7x8@weirdfishes> <YF8eL0dmSh6H8HX2@ceres.zyxst.net> <YF9YE282kOWN7ubr@weirdfishes> <YGMq6i%2BUIhNANHXW@weirdfishes> <YGQ6IyE6B31a6EV0@weirdfishes> <3c00c109-ed5a-496c-9339-22b3dc31747a@www.fastmail.com>
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On Fri, Apr 02, 2021 at 08:29:43PM +0000, Dave Cottlehuber wrote: > Does the issue also go away if you use `TSC-slow` ? I haven't, I can try it out. Yeah TSC-slow is poorly rated (-100) but scrubbing my zroot is much faster with it compared to ACPI-fast (rated at 900).. TSC-slow: scan: scrub repaired 0B in 00:00:12 with 0 errors on Fri Apr 2 22:37:06 2021 scan: scrub repaired 0B in 00:00:09 with 0 errors on Fri Apr 2 22:41:17 2021 scan: scrub repaired 0B in 00:00:09 with 0 errors on Fri Apr 2 22:41:40 2021 ACPI-fast: scan: scrub repaired 0B in 00:03:33 with 0 errors on Fri Apr 2 22:40:47 2021 scan: scrub repaired 0B in 00:03:29 with 0 errors on Fri Apr 2 22:46:14 2021 scan: scrub repaired 0B in 00:03:38 with 0 errors on Fri Apr 2 22:49:52 2021 So really ACPI-fast is not appropriately named, at least under KVM. Same thing as HPET... TSC-slow looks as good as kvmclock based on that simple benchmark but I guess there's a reason why it's at the bottom of the pile. > I investigated exactly this issue yesterday[1], and it's great to see Bryan's patch > resurrected, I will try it here and report back too. > > [1]: https://hackmd.io/HhYlbsDJTpCWHSwlrwrY_w FYI I created a new revision to have that patch merged (and there's a better version of it there): https://reviews.freebsd.org/D29531 Honestly the kvmclock patch is a game changer but I look forward to hearing your feedback. -- Mathieu Chouquet-Stringer The sun itself sees not till heaven clears. -- William Shakespeare --
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