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From: Patrick Steinhardt <ps@pks.im>
To: Junio C Hamano <gitster@pobox.com>
Cc: "Derrick Stolee" <stolee@gmail.com>,
	git@vger.kernel.org, "Jeff King" <peff@peff.net>,
	"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Subject: Re: [PATCH 1/6] fetch: speed up lookup of want refs via commit-graph
Date: Mon, 23 Aug 2021 08:46:27 +0200	[thread overview]
Message-ID: <YSNEQ9R0TDUNPZPM@ncase> (raw)
In-Reply-To: <xmqq7dggvxup.fsf@gitster.g>

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On Fri, Aug 20, 2021 at 10:18:22AM -0700, Junio C Hamano wrote:
> Derrick Stolee <stolee@gmail.com> writes:
> 
> > I do worry about the case where annotated tags greatly outnumber
> > branches, so this binary search is extra overhead and the performance
> > may degrade. Would it be worth checking the ref to see if it lies
> > within "refs/heads/" (or even _not_ in "refs/tags/") before doing
> > this commit-graph check?
> 
> Ah, clever.

Good idea. Benchmarks for my test repository (which definitely isn't
representative, but it's at least some numbers) show that restricting to
"refs/heads/" diminishes almost all the gains, while restricting to
everything but "refs/tags/" performs almost the same (it's a tiny bit
slower, probably because of the added string comparisons):

    Benchmark #1: all refs: git-fetch
      Time (mean ± σ):     32.959 s ±  0.282 s    [User: 29.801 s, System: 5.137 s]
      Range (min … max):   32.760 s … 33.158 s    2 runs

    Benchmark #2: refs/heads: git-fetch
      Time (mean ± σ):     56.955 s ±  0.002 s    [User: 53.447 s, System: 5.362 s]
      Range (min … max):   56.953 s … 56.957 s    2 runs

    Benchmark #3: !refs/tags: git-fetch
      Time (mean ± σ):     33.447 s ±  0.003 s    [User: 30.160 s, System: 5.027 s]
      Range (min … max):   33.444 s … 33.449 s    2 runs

    Summary
      'all refs: git-fetch' ran
        1.01 ± 0.01 times faster than '!refs/tags: git-fetch'
        1.73 ± 0.01 times faster than 'refs/heads: git-fetch'

This is easily explained by the fact that the test repo has most of its
refs neither in "refs/tags/" nor in "refs/heads/", but rather in special
namespaces like "refs/merge-requests/", "refs/environments/" or
"refs/keep-around/".

I like the idea of excluding "refs/tags/" though: as you point out,
chances are high that these don't point to commits but to annotated tags
instead. So I'll go with that, thanks!

Patrick

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  reply	other threads:[~2021-08-23  6:46 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-20 10:08 [PATCH 0/6] Speed up mirror-fetches with many refs Patrick Steinhardt
2021-08-20 10:08 ` [PATCH 1/6] fetch: speed up lookup of want refs via commit-graph Patrick Steinhardt
2021-08-20 14:27   ` Derrick Stolee
2021-08-20 17:18     ` Junio C Hamano
2021-08-23  6:46       ` Patrick Steinhardt [this message]
2021-08-25 14:12         ` Derrick Stolee
2021-08-20 10:08 ` [PATCH 2/6] fetch: avoid unpacking headers in object existence check Patrick Steinhardt
2021-08-25 23:44   ` Ævar Arnfjörð Bjarmason
2021-08-20 10:08 ` [PATCH 3/6] connected: refactor iterator to return next object ID directly Patrick Steinhardt
2021-08-20 14:32   ` Derrick Stolee
2021-08-20 17:43     ` Junio C Hamano
2021-08-20 17:43   ` René Scharfe
2021-08-23  6:47     ` Patrick Steinhardt
2021-08-20 10:08 ` [PATCH 4/6] fetch-pack: optimize loading of refs via commit graph Patrick Steinhardt
2021-08-20 14:37   ` Derrick Stolee
2021-08-20 10:08 ` [PATCH 5/6] fetch: refactor fetch refs to be more extendable Patrick Steinhardt
2021-08-20 14:41   ` Derrick Stolee
2021-08-20 10:08 ` [PATCH 6/6] fetch: avoid second connectivity check if we already have all objects Patrick Steinhardt
2021-08-20 14:47   ` Derrick Stolee
2021-08-23  6:52     ` Patrick Steinhardt
2021-08-20 14:50 ` [PATCH 0/6] Speed up mirror-fetches with many refs Derrick Stolee
2021-08-21  0:09 ` Junio C Hamano
2021-08-24 10:36 ` [PATCH v2 0/7] " Patrick Steinhardt
2021-08-24 10:36   ` [PATCH v2 1/7] fetch: speed up lookup of want refs via commit-graph Patrick Steinhardt
2021-08-25 14:16     ` Derrick Stolee
2021-08-24 10:37   ` [PATCH v2 2/7] fetch: avoid unpacking headers in object existence check Patrick Steinhardt
2021-08-24 10:37   ` [PATCH v2 3/7] connected: refactor iterator to return next object ID directly Patrick Steinhardt
2021-08-24 10:37   ` [PATCH v2 4/7] fetch-pack: optimize loading of refs via commit graph Patrick Steinhardt
2021-08-24 10:37   ` [PATCH v2 5/7] fetch: refactor fetch refs to be more extendable Patrick Steinhardt
2021-08-25 14:19     ` Derrick Stolee
2021-09-01 12:48       ` Patrick Steinhardt
2021-08-24 10:37   ` [PATCH v2 6/7] fetch: merge fetching and consuming refs Patrick Steinhardt
2021-08-25 14:26     ` Derrick Stolee
2021-09-01 12:49       ` Patrick Steinhardt
2021-08-24 10:37   ` [PATCH v2 7/7] fetch: avoid second connectivity check if we already have all objects Patrick Steinhardt
2021-08-24 22:48   ` [PATCH v2 0/7] Speed up mirror-fetches with many refs Junio C Hamano
2021-08-25  6:04     ` Patrick Steinhardt
2021-08-25 14:27   ` Derrick Stolee
2021-09-01 13:09 ` [PATCH v3 " Patrick Steinhardt
2021-09-01 13:09   ` [PATCH v3 1/7] fetch: speed up lookup of want refs via commit-graph Patrick Steinhardt
2021-09-01 13:09   ` [PATCH v3 2/7] fetch: avoid unpacking headers in object existence check Patrick Steinhardt
2021-09-01 13:09   ` [PATCH v3 3/7] connected: refactor iterator to return next object ID directly Patrick Steinhardt
2021-09-01 13:09   ` [PATCH v3 4/7] fetch-pack: optimize loading of refs via commit graph Patrick Steinhardt
2021-09-01 13:09   ` [PATCH v3 5/7] fetch: refactor fetch refs to be more extendable Patrick Steinhardt
2021-09-01 13:10   ` [PATCH v3 6/7] fetch: merge fetching and consuming refs Patrick Steinhardt
2021-09-01 13:10   ` [PATCH v3 7/7] fetch: avoid second connectivity check if we already have all objects Patrick Steinhardt
2021-09-01 19:58   ` [PATCH v3 0/7] Speed up mirror-fetches with many refs Junio C Hamano
2021-09-08  0:08     ` Junio C Hamano

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