Date: Tue, 23 Mar 2021 01:27:00 +0100 From: Mathieu Chouquet-Stringer <me+freebsd@mathieu.digital> To: Martin Simmons <martin@lispworks.com> Cc: freebsd-fs@freebsd.org Subject: Re: Scrub incredibly slow with 13.0-RC3 (as well as RC1 & 2) Message-ID: <YFk11A/j7URClN/l@weirdfishes> In-Reply-To: <YFi6Lwh3ISn8UMvS@weirdfishes> References: <YFhuxr0qRzchA7x8@weirdfishes> <202103221515.12MFFHRK015188@higson.cam.lispworks.com> <YFi6Lwh3ISn8UMvS@weirdfishes>
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On Mon, Mar 22, 2021 at 04:39:27PM +0100, Mathieu Chouquet-Stringer wrote:
> Hello Martin,
>
> Thanks for taking the time to reply to me.
>
> On Mon, Mar 22, 2021 at 03:15:17PM +0000, Martin Simmons wrote:
> > You could try:
> >
> > procstat -kk 0
> >
> > to get an overview of what the kernel threads are doing.
Exploring some more with top -SH, it seems that's my thread:
31 root -8 - 0B 3984K CPU7 7 38:14 99.92% zfskern{dsl_scan_iss_0}
That's the only busy thing on this OS and I know it's the one I see in
htop because I see it ping-ponging on different CPUs.
Seeing dsl_scan_iss led me to there:
https://github.com/openzfs/zfs/blob/64e0fe14fff465604952d576051ca80c2f1be898/module/zfs/dsl_scan.c
And that led me to reading about vfs.zfs.scan_legacy:
https://openzfs.github.io/openzfs-docs/Performance%20and%20Tuning/Module%20Parameters.html?highlight=scan_mem_lim_fact#zfs-scan-legacy
I killed the current scrub, put vfs.zfs.scan_legacy=1 in sysctl.conf,
rebooted and restarted it, it's already telling me it'll finish quicker
than the one which was running and wich had already done 10%. It's been
running for 22 minutes now.
scan: scrub in progress since Tue Mar 23 01:03:09 2021
63.0G scanned at 87.5M/s, 63.0G issued at 87.5M/s, 24.5T total
0B repaired, 0.25% done, 3 days 09:14:15 to go
I'll let it run overnight and I'll check back tomorrow: I mean you
can't trust the progress bar...
--
Mathieu Chouquet-Stringer
The sun itself sees not till heaven clears.
-- William Shakespeare --
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