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From: Junio C Hamano <gitster@pobox.com>
To: Jeff King <peff@peff.net>
Cc: Victoria Dye <vdye@github.com>,
	git@vger.kernel.org, Phillip Wood <phillip.wood123@gmail.com>
Subject: Re: [PATCH 2/3] read-cache: read on-disk entries in byte order
Date: Thu, 29 Sep 2022 08:47:24 -0700	[thread overview]
Message-ID: <xmqqczbep4hf.fsf@gitster.g> (raw)
In-Reply-To: <YzWBEoRkCmbUkIs8@coredump.intra.peff.net> (Jeff King's message of "Thu, 29 Sep 2022 07:27:14 -0400")

Jeff King <peff@peff.net> writes:

> On Wed, Sep 28, 2022 at 12:21:15AM -0400, Jeff King wrote:
>
>> The downside is that we're copying the data an extra time. It's not very
>> much data, and it's all fixed size, so the compiler should be able to do
>> a reasonable job of optimizing here. But I didn't time the potential
>> impact.
> ...
>   Summary
>     './test-tool.old read-cache 1000' ran
>       1.11 ± 0.04 times faster than './test-tool.new read-cache 1000'
>
> I think that's probably the nail in the coffin for my proposed approach.
> To be fair, it's only .3ms extra for a normal program which reads the
> index once. That's not that big in absolute numbers. But there are
> larger index files in the wild. And the improvement in simplicity and
> readability is simply not that great.

Thanks for the due diligence.  This result may be an indication of
how efficient the existing code is, but it is a bit surprising that
one more copy of the stat_data struct makes that much difference.


  reply	other threads:[~2022-09-29 15:48 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-27 21:11 What's cooking in git.git (Sep 2022, #08; Tue, 27) Junio C Hamano
2022-09-28  1:52 ` Victoria Dye
2022-09-28  4:18   ` vd/fix-unaligned-read-index-v4, was " Jeff King
2022-09-28  4:19     ` [PATCH 1/3] pack-bitmap: make read_be32() public Jeff King
2022-09-28  4:21     ` [PATCH 2/3] read-cache: read on-disk entries in byte order Jeff King
2022-09-29 11:27       ` Jeff King
2022-09-29 15:47         ` Junio C Hamano [this message]
2022-09-28  4:23     ` [PATCH 3/3] read-cache: use read_be32() in create_from_disk() Jeff King
2022-09-28 16:41     ` vd/fix-unaligned-read-index-v4, was Re: What's cooking in git.git (Sep 2022, #08; Tue, 27) Junio C Hamano
2022-09-28 17:01       ` Ævar Arnfjörð Bjarmason
2022-09-28 17:41         ` Junio C Hamano

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