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From: Derrick Stolee <stolee@gmail.com>
To: Derrick Stolee via GitGitGadget <gitgitgadget@gmail.com>,
	git@vger.kernel.org
Cc: gitster@pobox.com, peff@peff.net, git@jeffhostetler.com,
	Derrick Stolee <derrickstolee@github.com>,
	Derrick Stolee <dstolee@microsoft.com>
Subject: Re: [PATCH 2/3] read-cache: use hashfile instead of git_hash_ctx
Date: Mon, 29 Mar 2021 15:10:27 -0400	[thread overview]
Message-ID: <244d8b93-9d53-d660-ce08-d8b2362f75a8@gmail.com> (raw)
In-Reply-To: <8b368872-bb36-db61-20d7-47aa5af0ec37@gmail.com>

On 3/29/2021 11:04 AM, Derrick Stolee wrote:
> On 3/26/2021 3:12 PM, Derrick Stolee via GitGitGadget wrote:
>>  
>> -	if (ce_flush(&c, newfd, istate->oid.hash))
>> -		return -1;
>> +	finalize_hashfile(f, istate->oid.hash, CSUM_FSYNC | CSUM_HASH_IN_STREAM);
>>  	if (close_tempfile_gently(tempfile)) {
>>  		error(_("could not close '%s'"), get_tempfile_path(tempfile));
>>  		return -1;
> 
> It was bothering me all weekend why this change made index writes
> slower. The reason was this CSUM_FSYNC. Other performance measurement
> (instructions, branches, branch misses, etc.) are all really close to
> the old code, so this I/O is the only explanation. And truly, it is
> the case.
> 
> It seems that we avoid an fsync() on the index exactly for this perf
> reason, but we don't on other applications of the hashfile API because
> writes are not critical paths.
> 
> I'll update this series in a v2 soon that has some other improvements
> that I noticed while digging deep into things.

Small update: the pull request [1] has the latest changes that I
think will work for these needs. However, they will conflict with
the upcoming changes to ds/sparse-index to use index extensions.

[1] https://github.com/gitgitgadget/git/pull/916

I'll pause this series and re-send on top of ds/sparse-index
after it solidifies.

Thanks,
-Stolee

  reply	other threads:[~2021-03-29 19:11 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-26 19:12 [PATCH 0/3] Convert index writes to use hashfile API Derrick Stolee via GitGitGadget
2021-03-26 19:12 ` [PATCH 1/3] csum-file: add nested_hashfile() Derrick Stolee via GitGitGadget
2021-03-26 19:12 ` [PATCH 2/3] read-cache: use hashfile instead of git_hash_ctx Derrick Stolee via GitGitGadget
2021-03-29 15:04   ` Derrick Stolee
2021-03-29 19:10     ` Derrick Stolee [this message]
2021-03-26 19:12 ` [PATCH 3/3] read-cache: delete unused hashing methods Derrick Stolee via GitGitGadget
2021-03-26 20:16 ` [PATCH 0/3] Convert index writes to use hashfile API Derrick Stolee
2021-05-17 12:24 ` [PATCH v2 0/4] " Derrick Stolee via GitGitGadget
2021-05-17 12:24   ` [PATCH v2 1/4] hashfile: use write_in_full() Derrick Stolee via GitGitGadget
2021-05-17 12:24   ` [PATCH v2 2/4] csum-file.h: increase hashfile buffer size Derrick Stolee via GitGitGadget
2021-05-17 21:54     ` Junio C Hamano
2021-05-18  7:33       ` Jeff King
2021-05-18 14:44         ` Derrick Stolee
2021-05-18  7:31     ` Jeff King
2021-05-18  7:42       ` Jeff King
2021-05-17 12:24   ` [PATCH v2 3/4] read-cache: use hashfile instead of git_hash_ctx Derrick Stolee via GitGitGadget
2021-05-17 22:13     ` Junio C Hamano
2021-05-18 14:16       ` Derrick Stolee
2021-05-17 12:24   ` [PATCH v2 4/4] read-cache: delete unused hashing methods Derrick Stolee via GitGitGadget
2021-05-18 18:32   ` [PATCH v3 0/4] Convert index writes to use hashfile API Derrick Stolee via GitGitGadget
2021-05-18 18:32     ` [PATCH v3 1/4] hashfile: use write_in_full() Derrick Stolee via GitGitGadget
2021-05-18 18:32     ` [PATCH v3 2/4] csum-file.h: increase hashfile buffer size Derrick Stolee via GitGitGadget
2021-11-25 12:14       ` t4216-log-bloom.sh fails with -v (but not --verbose-log) Ævar Arnfjörð Bjarmason
2021-11-26  4:08         ` Jeff King
2021-11-29 13:49           ` Derrick Stolee
2021-05-18 18:32     ` [PATCH v3 3/4] read-cache: use hashfile instead of git_hash_ctx Derrick Stolee via GitGitGadget
2021-05-18 18:32     ` [PATCH v3 4/4] read-cache: delete unused hashing methods Derrick Stolee via GitGitGadget

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