From: Jeff King <peff@peff.net>
To: Jacob Vosmaer <jacob@gitlab.com>
Cc: git@vger.kernel.org
Subject: Re: [PATCH 1/1] ls-refs.c: minimize number of refs visited
Date: Tue, 19 Jan 2021 17:53:56 -0500 [thread overview]
Message-ID: <YAdjBC7z2eE1Z0uk@coredump.intra.peff.net> (raw)
In-Reply-To: <20210119144251.27924-2-jacob@gitlab.com>
On Tue, Jan 19, 2021 at 03:42:51PM +0100, Jacob Vosmaer wrote:
> The previous implementation of ls-refs would perform exactly one ref
> walk, matching each ref against the prefixes (if any) provided by the
> user. This can be expensive if there are a lot of refs and the user
> only cares about a small subset of them.
>
> In this patch we analyze the prefixes provided by the user and build a
> minimal set of disjoint prefixes that contains all of them. We then do
> a ref walk for each of these minimal prefixes.
Thanks for posting this. I have a vague recollection that we considered
this either when we did the for-each-ref prefixes, or when we added
ls-refs prefixes, but I can't seem to find either. At any rate, at
GitHub we haven't generally found it to be a problem because our
horrifically-large repos tend to be aggregated alternates repos, not the
ones people serve upload-pack out of (though I did just time it, and
some of our largest repos should save a few hundred milliseconds per
advertisement, which is certainly not nothing).
I do think we should reuse the code from ref-filter, as Taylor showed.
> This commit also fixes a bug in ls-refs.c that was not triggered
> before: we were using a strvec set to zero, which is not how you are
> supposed to initialize a strvec. We now call strvec_init after zeroing.
Good catch. It didn't matter until now because nobody relied on having a
NULL entry when no prefix had been added (instead, they always iterated
over prefixes->nr). IMHO that is worth fixing as a separate commit.
-Peff
next prev parent reply other threads:[~2021-01-19 22:57 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-19 14:42 [PATCH 0/1] ls-refs.c: minimize number of refs visited Jacob Vosmaer
2021-01-19 14:42 ` [PATCH 1/1] " Jacob Vosmaer
2021-01-19 16:12 ` Taylor Blau
2021-01-19 17:42 ` Jacob Vosmaer
2021-01-19 18:19 ` [PATCH 0/2] ls-refs: only traverse through longest common ref prefix Taylor Blau
2021-01-19 18:19 ` [PATCH 1/2] refs: expose 'for_each_fullref_in_prefixes' Taylor Blau
2021-01-19 18:19 ` [PATCH 2/2] ls-refs.c: traverse longest common ref prefix Taylor Blau
2021-01-19 23:09 ` Jeff King
2021-01-19 23:52 ` Taylor Blau
2021-01-20 0:08 ` Jeff King
2021-01-20 11:00 ` Jacob Vosmaer
2021-01-20 16:04 ` [PATCH v2 0/3] ls-refs: traverse prefixes of disjoint "ref-prefix" sets Taylor Blau
2021-01-20 16:04 ` [PATCH v2 1/3] refs: expose 'for_each_fullref_in_prefixes' Taylor Blau
2021-01-20 19:56 ` Jeff King
2021-01-20 20:12 ` Taylor Blau
2021-01-23 2:59 ` Junio C Hamano
2021-01-25 1:35 ` Taylor Blau
2021-01-20 16:04 ` [PATCH v2 2/3] ls-refs.c: initialize 'prefixes' before using it Taylor Blau
2021-01-20 19:58 ` Jeff King
2021-01-20 20:13 ` Taylor Blau
2021-01-20 21:50 ` Jacob Vosmaer
2021-01-20 16:04 ` [PATCH v2 3/3] ls-refs.c: traverse prefixes of disjoint "ref-prefix" sets Taylor Blau
2021-01-23 17:55 ` [PATCH v2 0/3] ls-refs: " Junio C Hamano
2021-01-19 19:09 ` [PATCH 1/1] ls-refs.c: minimize number of refs visited Taylor Blau
2021-01-19 21:59 ` Jeff King
2021-01-19 22:15 ` Jeff King
2021-01-19 22:23 ` Taylor Blau
2021-01-19 22:52 ` Jeff King
2021-01-19 22:59 ` Jeff King
2021-01-19 23:02 ` Taylor Blau
2021-01-19 22:53 ` Jeff King [this message]
2021-01-19 23:00 ` Taylor Blau
2021-01-19 23:11 ` Jeff King
2021-01-20 10:40 ` Jacob Vosmaer
2021-01-20 10:44 ` Jacob Vosmaer
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