From: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
To: Neeraj Singh <nksingh85@gmail.com>
Cc: Junio C Hamano <gitster@pobox.com>,
"Neeraj K. Singh via GitGitGadget" <gitgitgadget@gmail.com>,
Git List <git@vger.kernel.org>,
Johannes Schindelin <Johannes.Schindelin@gmx.de>,
Jeff King <peff@peff.net>,
Jeff Hostetler <jeffhost@microsoft.com>,
Christoph Hellwig <hch@lst.de>,
"Neeraj K. Singh" <neerajsi@microsoft.com>
Subject: Re: [PATCH v2 0/6] Implement a batched fsync option for core.fsyncObjectFiles
Date: Wed, 08 Sep 2021 21:23:05 +0200 [thread overview]
Message-ID: <87k0jqhnji.fsf@evledraar.gmail.com> (raw)
In-Reply-To: <CANQDOddQsf4Jj+634mdnJXaPG=2idCbCHd1iXO2qm1EMGcDmXg@mail.gmail.com>
On Wed, Sep 08 2021, Neeraj Singh wrote:
> On Tue, Sep 7, 2021 at 11:44 PM Junio C Hamano <gitster@pobox.com> wrote:
>>
>> Neeraj Singh <nksingh85@gmail.com> writes:
>>
>> > BTW, I updated the github PR to enable batch mode everywhere, and all
>> > the tests passed, which is good news to me.
>>
>> I doubt that fsyncObjectFiles is something we can reliably test in
>> CI, either with the new batched thing or with the original "when we
>> close one, make sure the changes hit the disk platter" approach. So
>> I am not sure what conclusion we should draw from such an experiment,
>> other than "ok, it compiles cleanly." After all, unless we cause
>> system crashes, what we thought we have written and close(2) would
>> be seen by another process that we spawn after that, with or without
>> sync, no?
>
> The main failure mode I was worried about is that some test or other part
> of Git is relying on a loose object being immediately available after it is
> added to the ODB. With batch mode, the loose objects aren't actually
> available until the bulk checkin is unplugged.
>
> I agree that it is not easy to test whether the data is actually going
> to durable
> storage at the expected time. FWIW, I did take a disk IO trace on Windows to
> verify that we are issuing disk writes and flushes at the right time.
> But that's a
> one-time test that would be hard to make automated.
I have some semi-related patches I need to dig up and finish sometime
which add a "git gc" test mode to the test suite, i.e. any time we call
"git gc --auto" it will go ahead and actually run, and some adversarial
options to run always, right away, prune with --expire=now. It found
some false positives, but also some genuine races and bugs at the time.
Similarly, I think a good longer term goal for better fsync() and data
integrity in git is to refactor the various codepaths where we write to
disk (grepping for fsync_or_die() is a good start to find those) to all
live in one place, we could then easily instrument that code to run in a
hostile test mode.
E.g. make anything that expects to write out a "foo" file actually write
out "foo.not-synced-yet" as long as fsync() etc. hasn't been called, or
with signals/timers/atexit() handlers fake up known FS edge cases such
as a write of "foo" only renaming "foo.not-synced-yet" to "foo" 1s after
the last close() call not followed by an fsync, etc.
Anyway, I expect given your occupation that you may have better ideas in
that area, presumably needing to instrument and test behavior under I/O
pressure, deferred syncs etc. is something mature FS's need to deal with
as part of their own regression tests...
1. https://lore.kernel.org/git/cover-v2-0.4-0000000000-20210908T003631Z-avarab@gmail.com/
next prev parent reply other threads:[~2021-09-08 19:31 UTC|newest]
Thread overview: 160+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-25 1:51 [PATCH 0/2] [RFC] Implement a bulk-checkin option for core.fsyncObjectFiles Neeraj K. Singh via GitGitGadget
2021-08-25 1:51 ` [PATCH 1/2] object-file: use futimes rather than utime Neeraj Singh via GitGitGadget
2021-08-25 13:51 ` Johannes Schindelin
2021-08-25 22:08 ` Neeraj Singh
2021-08-25 1:51 ` [PATCH 2/2] core.fsyncobjectfiles: batch disk flushes Neeraj Singh via GitGitGadget
2021-08-25 5:38 ` Christoph Hellwig
2021-08-25 17:40 ` Neeraj Singh
2021-08-26 5:54 ` Christoph Hellwig
2021-08-25 16:11 ` Ævar Arnfjörð Bjarmason
2021-08-26 0:49 ` Neeraj Singh
2021-08-26 5:50 ` Christoph Hellwig
2021-08-28 0:20 ` Neeraj Singh
2021-08-28 6:57 ` Christoph Hellwig
2021-08-31 19:59 ` Neeraj Singh
2021-09-01 5:09 ` Christoph Hellwig
2021-08-26 5:57 ` Christoph Hellwig
2021-08-25 18:52 ` Johannes Schindelin
2021-08-25 21:26 ` Junio C Hamano
2021-08-26 1:19 ` Neeraj Singh
2021-08-25 16:58 ` [PATCH 0/2] [RFC] Implement a bulk-checkin option for core.fsyncObjectFiles Neeraj Singh
2021-08-27 23:49 ` [PATCH v2 0/6] Implement a batched fsync " Neeraj K. Singh via GitGitGadget
2021-08-27 23:49 ` [PATCH v2 1/6] object-file: use futimens rather than utime Neeraj Singh via GitGitGadget
2021-08-27 23:49 ` [PATCH v2 2/6] bulk-checkin: rename 'state' variable and separate 'plugged' boolean Neeraj Singh via GitGitGadget
2021-08-27 23:49 ` [PATCH v2 3/6] core.fsyncobjectfiles: batched disk flushes Neeraj Singh via GitGitGadget
2021-08-27 23:49 ` [PATCH v2 4/6] core.fsyncobjectfiles: add windows support for batch mode Neeraj Singh via GitGitGadget
2021-08-27 23:49 ` [PATCH v2 5/6] update-index: use the bulk-checkin infrastructure Neeraj Singh via GitGitGadget
2021-08-27 23:49 ` [PATCH v2 6/6] core.fsyncobjectfiles: performance tests for add and stash Neeraj Singh via GitGitGadget
2021-09-07 19:44 ` [PATCH v2 0/6] Implement a batched fsync option for core.fsyncObjectFiles Neeraj Singh
2021-09-07 19:50 ` Ævar Arnfjörð Bjarmason
2021-09-07 19:54 ` Randall S. Becker
2021-09-08 0:54 ` Neeraj Singh
2021-09-08 1:22 ` Ævar Arnfjörð Bjarmason
2021-09-08 14:04 ` Randall S. Becker
2021-09-08 19:01 ` Neeraj Singh
2021-09-08 0:55 ` Neeraj Singh
2021-09-08 6:44 ` Junio C Hamano
2021-09-08 6:49 ` Christoph Hellwig
2021-09-08 13:57 ` Randall S. Becker
2021-09-08 14:13 ` 'Christoph Hellwig'
2021-09-08 14:25 ` Randall S. Becker
2021-09-08 16:34 ` Neeraj Singh
2021-09-08 19:12 ` Junio C Hamano
2021-09-08 19:20 ` Neeraj Singh
2021-09-08 19:23 ` Ævar Arnfjörð Bjarmason [this message]
2021-09-14 3:38 ` [PATCH v3 " Neeraj K. Singh via GitGitGadget
2021-09-14 3:38 ` [PATCH v3 1/6] bulk-checkin: rename 'state' variable and separate 'plugged' boolean Neeraj Singh via GitGitGadget
2021-09-14 3:38 ` [PATCH v3 2/6] core.fsyncobjectfiles: batched disk flushes Neeraj Singh via GitGitGadget
2021-09-14 10:39 ` Bagas Sanjaya
2021-09-14 19:05 ` Neeraj Singh
2021-09-14 19:34 ` Junio C Hamano
2021-09-14 20:33 ` Junio C Hamano
2021-09-15 4:55 ` Neeraj Singh
2021-09-14 3:38 ` [PATCH v3 3/6] core.fsyncobjectfiles: add windows support for batch mode Neeraj Singh via GitGitGadget
2021-09-14 3:38 ` [PATCH v3 4/6] update-index: use the bulk-checkin infrastructure Neeraj Singh via GitGitGadget
2021-09-14 19:35 ` Junio C Hamano
2021-09-14 3:38 ` [PATCH v3 5/6] core.fsyncobjectfiles: performance tests for add and stash Neeraj Singh via GitGitGadget
2021-09-14 3:38 ` [PATCH v3 6/6] core.fsyncobjectfiles: enable batch mode for testing Neeraj Singh via GitGitGadget
2021-09-15 16:21 ` Junio C Hamano
2021-09-15 22:43 ` Neeraj Singh
2021-09-15 23:12 ` Junio C Hamano
2021-09-16 6:19 ` Junio C Hamano
2021-09-14 5:49 ` [PATCH v3 0/6] Implement a batched fsync option for core.fsyncObjectFiles Christoph Hellwig
2021-09-20 22:15 ` [PATCH v4 " Neeraj K. Singh via GitGitGadget
2021-09-20 22:15 ` [PATCH v4 1/6] bulk-checkin: rename 'state' variable and separate 'plugged' boolean Neeraj Singh via GitGitGadget
2021-09-20 22:15 ` [PATCH v4 2/6] core.fsyncobjectfiles: batched disk flushes Neeraj Singh via GitGitGadget
2021-09-21 23:16 ` Ævar Arnfjörð Bjarmason
2021-09-22 1:23 ` Neeraj Singh
2021-09-22 2:02 ` Ævar Arnfjörð Bjarmason
2021-09-22 19:46 ` Neeraj Singh
2021-09-20 22:15 ` [PATCH v4 3/6] core.fsyncobjectfiles: add windows support for batch mode Neeraj Singh via GitGitGadget
2021-09-21 23:42 ` Ævar Arnfjörð Bjarmason
2021-09-22 1:23 ` Neeraj Singh
2021-09-20 22:15 ` [PATCH v4 4/6] update-index: use the bulk-checkin infrastructure Neeraj Singh via GitGitGadget
2021-09-21 23:46 ` Ævar Arnfjörð Bjarmason
2021-09-22 1:27 ` Neeraj Singh
2021-09-23 22:32 ` Neeraj Singh
2021-09-20 22:15 ` [PATCH v4 5/6] core.fsyncobjectfiles: tests for batch mode Neeraj Singh via GitGitGadget
2021-09-21 23:54 ` Ævar Arnfjörð Bjarmason
2021-09-22 1:30 ` Neeraj Singh
2021-09-22 1:58 ` Ævar Arnfjörð Bjarmason
2021-09-22 17:55 ` Neeraj Singh
2021-09-22 20:01 ` Ævar Arnfjörð Bjarmason
2021-09-20 22:15 ` [PATCH v4 6/6] core.fsyncobjectfiles: performance tests for add and stash Neeraj Singh via GitGitGadget
2021-09-24 20:12 ` [PATCH v5 0/7] Implement a batched fsync option for core.fsyncObjectFiles Neeraj K. Singh via GitGitGadget
2021-09-24 20:12 ` [PATCH v5 1/7] object-file.c: do not rename in a temp odb Neeraj Singh via GitGitGadget
2021-09-24 20:12 ` [PATCH v5 2/7] bulk-checkin: rename 'state' variable and separate 'plugged' boolean Neeraj Singh via GitGitGadget
2021-09-24 20:12 ` [PATCH v5 3/7] core.fsyncobjectfiles: batched disk flushes Neeraj Singh via GitGitGadget
2021-09-24 21:47 ` Neeraj Singh
2021-09-24 20:12 ` [PATCH v5 4/7] update-index: use the bulk-checkin infrastructure Neeraj Singh via GitGitGadget
2021-09-24 21:49 ` Neeraj Singh
2021-09-24 20:12 ` [PATCH v5 5/7] unpack-objects: " Neeraj Singh via GitGitGadget
2021-09-24 20:12 ` [PATCH v5 6/7] core.fsyncobjectfiles: tests for batch mode Neeraj Singh via GitGitGadget
2021-09-24 20:12 ` [PATCH v5 7/7] core.fsyncobjectfiles: performance tests for add and stash Neeraj Singh via GitGitGadget
2021-09-24 23:31 ` [PATCH v5 0/7] Implement a batched fsync option for core.fsyncObjectFiles Neeraj Singh
2021-09-24 23:53 ` [PATCH v6 0/8] " Neeraj K. Singh via GitGitGadget
2021-09-24 23:53 ` [PATCH v6 1/8] object-file.c: do not rename in a temp odb Neeraj Singh via GitGitGadget
2021-09-24 23:53 ` [PATCH v6 2/8] bulk-checkin: rename 'state' variable and separate 'plugged' boolean Neeraj Singh via GitGitGadget
2021-09-24 23:53 ` [PATCH v6 3/8] core.fsyncobjectfiles: batched disk flushes Neeraj Singh via GitGitGadget
2021-09-25 3:15 ` Bagas Sanjaya
2021-09-27 0:27 ` Neeraj Singh
2021-09-24 23:53 ` [PATCH v6 4/8] core.fsyncobjectfiles: add windows support for batch mode Neeraj Singh via GitGitGadget
2021-09-27 20:07 ` Junio C Hamano
2021-09-27 20:55 ` Neeraj Singh
2021-09-27 21:03 ` Neeraj Singh
2021-09-27 23:53 ` Junio C Hamano
2021-09-24 23:53 ` [PATCH v6 5/8] update-index: use the bulk-checkin infrastructure Neeraj Singh via GitGitGadget
2021-09-24 23:53 ` [PATCH v6 6/8] unpack-objects: " Neeraj Singh via GitGitGadget
2021-09-24 23:53 ` [PATCH v6 7/8] core.fsyncobjectfiles: tests for batch mode Neeraj Singh via GitGitGadget
2021-09-24 23:53 ` [PATCH v6 8/8] core.fsyncobjectfiles: performance tests for add and stash Neeraj Singh via GitGitGadget
2021-09-28 23:32 ` [PATCH v7 0/9] Implement a batched fsync option for core.fsyncObjectFiles Neeraj K. Singh via GitGitGadget
2021-09-28 23:32 ` [PATCH v7 1/9] object-file.c: do not rename in a temp odb Neeraj Singh via GitGitGadget
2021-09-28 23:55 ` Jeff King
2021-09-29 0:10 ` Neeraj Singh
2021-09-28 23:32 ` [PATCH v7 2/9] tmp-objdir: new API for creating temporary writable databases Neeraj Singh via GitGitGadget
2021-09-29 8:41 ` Elijah Newren
2021-09-29 16:40 ` Neeraj Singh
2021-09-28 23:32 ` [PATCH v7 3/9] bulk-checkin: rename 'state' variable and separate 'plugged' boolean Neeraj Singh via GitGitGadget
2021-09-28 23:32 ` [PATCH v7 4/9] core.fsyncobjectfiles: batched disk flushes Neeraj Singh via GitGitGadget
2021-09-28 23:32 ` [PATCH v7 5/9] core.fsyncobjectfiles: add windows support for batch mode Neeraj Singh via GitGitGadget
2021-09-28 23:32 ` [PATCH v7 6/9] update-index: use the bulk-checkin infrastructure Neeraj Singh via GitGitGadget
2021-09-28 23:32 ` [PATCH v7 7/9] unpack-objects: " Neeraj Singh via GitGitGadget
2021-09-28 23:32 ` [PATCH v7 8/9] core.fsyncobjectfiles: tests for batch mode Neeraj Singh via GitGitGadget
2021-09-28 23:32 ` [PATCH v7 9/9] core.fsyncobjectfiles: performance tests for add and stash Neeraj Singh via GitGitGadget
2021-10-04 16:57 ` [PATCH v8 0/9] Implement a batched fsync option for core.fsyncObjectFiles Neeraj K. Singh via GitGitGadget
2021-10-04 16:57 ` [PATCH v8 1/9] tmp-objdir: new API for creating temporary writable databases Neeraj Singh via GitGitGadget
2021-10-04 16:57 ` [PATCH v8 2/9] tmp-objdir: disable ref updates when replacing the primary odb Neeraj Singh via GitGitGadget
2021-10-04 16:57 ` [PATCH v8 3/9] bulk-checkin: rename 'state' variable and separate 'plugged' boolean Neeraj Singh via GitGitGadget
2021-10-04 16:57 ` [PATCH v8 4/9] core.fsyncobjectfiles: batched disk flushes Neeraj Singh via GitGitGadget
2021-10-04 16:57 ` [PATCH v8 5/9] core.fsyncobjectfiles: add windows support for batch mode Neeraj Singh via GitGitGadget
2021-10-04 16:57 ` [PATCH v8 6/9] update-index: use the bulk-checkin infrastructure Neeraj Singh via GitGitGadget
2021-10-04 16:57 ` [PATCH v8 7/9] unpack-objects: " Neeraj Singh via GitGitGadget
2021-10-04 16:57 ` [PATCH v8 8/9] core.fsyncobjectfiles: tests for batch mode Neeraj Singh via GitGitGadget
2021-10-04 16:57 ` [PATCH v8 9/9] core.fsyncobjectfiles: performance tests for add and stash Neeraj Singh via GitGitGadget
2021-11-15 23:50 ` [PATCH v9 0/9] Implement a batched fsync option for core.fsyncObjectFiles Neeraj K. Singh via GitGitGadget
2021-11-15 23:50 ` [PATCH v9 1/9] tmp-objdir: new API for creating temporary writable databases Neeraj Singh via GitGitGadget
2021-11-30 21:27 ` Elijah Newren
2021-11-30 21:52 ` Neeraj Singh
2021-11-30 22:36 ` Elijah Newren
2021-11-15 23:50 ` [PATCH v9 2/9] tmp-objdir: disable ref updates when replacing the primary odb Neeraj Singh via GitGitGadget
2021-11-16 7:23 ` Ævar Arnfjörð Bjarmason
2021-11-16 20:38 ` Neeraj Singh
2021-11-15 23:50 ` [PATCH v9 3/9] bulk-checkin: rename 'state' variable and separate 'plugged' boolean Neeraj Singh via GitGitGadget
2021-11-15 23:50 ` [PATCH v9 4/9] core.fsyncobjectfiles: batched disk flushes Neeraj Singh via GitGitGadget
2021-11-15 23:50 ` [PATCH v9 5/9] core.fsyncobjectfiles: add windows support for batch mode Neeraj Singh via GitGitGadget
2021-11-15 23:51 ` [PATCH v9 6/9] update-index: use the bulk-checkin infrastructure Neeraj Singh via GitGitGadget
2021-11-15 23:51 ` [PATCH v9 7/9] unpack-objects: " Neeraj Singh via GitGitGadget
2021-11-15 23:51 ` [PATCH v9 8/9] core.fsyncobjectfiles: tests for batch mode Neeraj Singh via GitGitGadget
2021-11-15 23:51 ` [PATCH v9 9/9] core.fsyncobjectfiles: performance tests for add and stash Neeraj Singh via GitGitGadget
2021-11-16 8:02 ` [PATCH v9 0/9] Implement a batched fsync option for core.fsyncObjectFiles Ævar Arnfjörð Bjarmason
2021-11-17 7:06 ` Neeraj Singh
2021-11-17 7:24 ` Ævar Arnfjörð Bjarmason
2021-11-18 5:03 ` Neeraj Singh
2021-12-01 14:15 ` Ævar Arnfjörð Bjarmason
2022-03-09 23:02 ` Ævar Arnfjörð Bjarmason
2022-03-10 1:16 ` Neeraj Singh
2022-03-10 14:01 ` Ævar Arnfjörð Bjarmason
2022-03-10 17:52 ` Neeraj Singh
2022-03-10 18:08 ` rsbecker
2022-03-10 18:43 ` Neeraj Singh
2022-03-10 18:48 ` rsbecker
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