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Date:      Wed, 23 Aug 2023 13:37:09 -0700
From:      Mark Millard <marklmi@yahoo.com>
To:        Alexander Motin <mav@FreeBSD.org>
Cc:        Current FreeBSD <freebsd-current@freebsd.org>
Subject:   Re: ZFS deadlock in 14
Message-ID:  <1AC87B79-6B65-402B-B65F-CCFFCC503861@yahoo.com>
In-Reply-To: <b8f819f0-9f6d-af87-64f9-35e37fbf4b2c@FreeBSD.org>
References:  <4FFAE432-21FE-4462-9162-9CC30A5D470A.ref@yahoo.com> <4FFAE432-21FE-4462-9162-9CC30A5D470A@yahoo.com> <b8f819f0-9f6d-af87-64f9-35e37fbf4b2c@FreeBSD.org>

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On Aug 23, 2023, at 11:40, Alexander Motin <mav@FreeBSD.org> wrote:

> On 22.08.2023 14:24, Mark Millard wrote:
>> Alexander Motin <mav_at_FreeBSD.org> wrote on
>> Date: Tue, 22 Aug 2023 16:18:12 UTC :
>>> I am waiting for final test results from George Wilson and then will
>>> request quick merge of both to zfs-2.2-release branch. Unfortunately
>>> there are still not many reviewers for the PR, since the code is not
>>> trivial, but at least with the test reports Brian Behlendorf and =
Mark
>>> Maybee seem to be OK to merge the two PRs into 2.2. If somebody else
>>> have tested and/or reviewed the PR, you may comment on it.
>> I had written to the list that when I tried to test the system
>> doing poudriere builds (initially with your patches) using
>> USE_TMPFS=3Dno so that zfs had to deal with all the file I/O, I
>> instead got only one builder that ended up active, the others
>> never reaching "Builder started":
>=20
>> Top was showing lots of "vlruwk" for the cpdup's. For example:
>> . . .
>>  362     0 root         40    0  27076Ki   13776Ki CPU19   19   4:23  =
 0.00% cpdup -i0 -o ref 32
>>  349     0 root         53    0  27076Ki   13776Ki vlruwk  22   4:20  =
 0.01% cpdup -i0 -o ref 31
>>  328     0 root         68    0  27076Ki   13804Ki vlruwk   8   4:30  =
 0.01% cpdup -i0 -o ref 30
>>  304     0 root         37    0  27076Ki   13792Ki vlruwk   6   4:18  =
 0.01% cpdup -i0 -o ref 29
>>  282     0 root         42    0  33220Ki   13956Ki vlruwk   8   4:33  =
 0.01% cpdup -i0 -o ref 28
>>  242     0 root         56    0  27076Ki   13796Ki vlruwk   4   4:28  =
 0.00% cpdup -i0 -o ref 27
>> . . .
>> But those processes did show CPU?? on occasion, as well as
>> *vnode less often. None of the cpdup's was stuck in
>> Removing your patches did not change the behavior.
>=20
> Mark, to me "vlruwk" looks like a limit on number of vnodes.  I was =
not deep in that area at least recently, so somebody with more =
experience there could try to diagnose it.  At very least it does not =
look related to the ZIL issue discussed in this thread, at least with =
the information provided, so I am not surprised that the mentioned =
patches do not affect it.

Thanks for the information. Good to know. I'll redirect this to be a =
different discussion.



=3D=3D=3D
Mark Millard
marklmi at yahoo.com




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