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From: Jeff Hostetler <git@jeffhostetler.com>
To: Derrick Stolee via GitGitGadget <gitgitgadget@gmail.com>,
	git@vger.kernel.org
Cc: gitster@pobox.com, me@ttaylorr.com,
	chakrabortyabhradeep79@gmail.com,
	Derrick Stolee <derrickstolee@github.com>
Subject: Re: [PATCH] pack-bitmap: remove trace2 region from hot path
Date: Tue, 27 Sep 2022 14:37:19 -0400	[thread overview]
Message-ID: <4c4954d8-82ea-8674-542e-865c514a7ae5@jeffhostetler.com> (raw)
In-Reply-To: <pull.1365.git.1663938034607.gitgitgadget@gmail.com>



On 9/23/22 9:00 AM, Derrick Stolee via GitGitGadget wrote:
> From: Derrick Stolee <derrickstolee@github.com>
> 
> The trace2 region around the call to lazy_bitmap_for_commit() in
> bitmap_for_commit() was added in 28cd730680d (pack-bitmap: prepare to
> read lookup table extension, 2022-08-14). While adding trace2 regions is
> typically helpful for tracking performance, this method is called
> possibly thousands of times as a commit walk explores commit history
> looking for a matching bitmap. When trace2 output is enabled, this
> region is emitted many times and performance is throttled by that
> output.
> 
> For now, remove these regions entirely.
> 
> This is a critical path, and it would be valuable to measure that the
> time spent in bitmap_for_commit() does not increase when using the
> commit lookup table. The best way to do that would be to use a mechanism
> that sums the time spent in a region and reports a single value at the
> end of the process. This technique was introduced but not merged by [1]
> so maybe this example presents some justification to revisit that
> approach.
> 
> [1] https://lore.kernel.org/git/pull.1099.v2.git.1640720202.gitgitgadget@gmail.com/

I'll dust off my "timers and counters" series, address the
various issues that were raised back in December, and resubmit.

Thanks for the reminder.
Jeff


      parent reply	other threads:[~2022-09-27 18:37 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-23 13:00 [PATCH] pack-bitmap: remove trace2 region from hot path Derrick Stolee via GitGitGadget
2022-09-23 17:05 ` Junio C Hamano
2022-09-23 17:25   ` Junio C Hamano
2022-09-23 17:36 ` Junio C Hamano
2022-09-23 18:07   ` Derrick Stolee
2022-09-23 19:17   ` Taylor Blau
2022-09-26 13:17 ` [PATCH v2] " Derrick Stolee via GitGitGadget
2022-09-26 15:01   ` Ævar Arnfjörð Bjarmason
2022-09-26 17:31     ` Derrick Stolee
2022-09-27 18:37 ` Jeff Hostetler [this message]

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