From: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
To: Junio C Hamano <gitster@pobox.com>
Cc: Bagas Sanjaya <bagasdotme@gmail.com>,
John Cai <johncai86@gmail.com>,
git@vger.kernel.org, me@ttaylorr.com, phillip.wood123@gmail.com,
e@80x24.org
Subject: Re: [RFC v3] cat-file: add a --stdin-cmd mode
Date: Tue, 01 Feb 2022 10:48:38 +0100 [thread overview]
Message-ID: <220201.86r18map8t.gmgdl@evledraar.gmail.com> (raw)
In-Reply-To: <xmqqpmo7ix0l.fsf@gitster.g>
On Mon, Jan 31 2022, Junio C Hamano wrote:
> Bagas Sanjaya <bagasdotme@gmail.com> writes:
>
>> On 29/01/22 01.33, John Cai wrote:
>>> Future improvements:
>>> - a non-trivial part of "cat-file --batch" time is spent
>>> on parsing its argument and seeing if it's a revision, ref etc. So we
>>> could add a command that only accepts a full-length 40
>>> character SHA-1.
>>
>> I think the full hash is actually revision name.
>
> There is no entry for "revision name" in Documentation/glossary-content.txt
> ;-)
>
> But to John, if you have a loop that feedseach line to get_oid(),
>
> while (getline(buf)) {
> struct object_id oid;
> if (get_oid(buf, &oid))
> warn and continue;
> use oid;
> }
>
> is it much slower than a mode that can ONLY handle a full object
> name input, i.e.
>
> while (getline(buf)) {
> struct object_id oid;
> if (get_oid_hex(buf, &oid))
> warn and continue;
> use oid;
> }
>
> when your input is restricted to full object names?
>
> get_oid() == repo_get_oid()
> -> get_oid_with_context()
> -> get_oid_with_context_1()
> -> get_oid_1()
> -> peel_onion()
> -> get_oid_basic()
> -> get_oid_hex()
> -> repo_dwim_ref()
>
> it seems that warn_ambiguous_refs and warn_on_object_refname_ambiguity
> we would waste time on refname discovery but I see cat-file already
> has some provision to disable this check. So when we do not need to
> call repo_dwim_ref(), do we still spend measurable cycles in this
> callchain?
For what it's worth I think this claim that we spend a non-trivial
amount of time on the difference between these two comes from me
originally. I'd had a chat with John about various things to try out in
such a "cat-file --batch" mode, and this was one of those things.
I tried instrumenting the relevant code in builtin/cat-file.c the other
(but forgot to reply to this thread), and whatever I'd found there at
the time (this was weeks/months ago) I couldn't reproduce.
So there's probably nothing worthwhile to check out here, i.e. the
trivial cost of get_oid_with_context() is probably nothing to worry
about.
next prev parent reply other threads:[~2022-02-01 9:51 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-28 18:33 [RFC v3] cat-file: add a --stdin-cmd mode John Cai
2022-01-31 11:44 ` Bagas Sanjaya
2022-01-31 18:24 ` Junio C Hamano
2022-02-01 9:48 ` Ævar Arnfjörð Bjarmason [this message]
2022-02-01 9:39 ` Christian Couder
2022-02-01 17:52 ` Taylor Blau
2022-02-01 19:27 ` John Cai
2022-02-01 20:14 ` Taylor Blau
[not found] ` <3FE1D509-8AD0-4F0E-9298-DFD3552A98EF@gmail.com>
2022-02-02 1:45 ` Taylor Blau
2022-02-02 13:11 ` John Cai
2022-02-01 10:43 ` Phillip Wood
2022-02-02 15:05 ` John Cai
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