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From: Eric Wong <>
To: Colin Stolley <>
Subject: hashmap vs khash? Re: [PATCH] packfile.c: speed up loading lots of packfiles.
Date: Thu, 28 Nov 2019 00:42:02 +0000
Message-ID: <20191128004202.GA25910@dcvr> (raw)
In-Reply-To: <>

Colin Stolley <> wrote:
> When loading packfiles on start-up, we traverse the internal packfile
> list once per file to avoid reloading packfiles that have already
> been loaded. This check runs in quadratic time, so for poorly
> maintained repos with a large number of packfiles, it can be pretty
> slow.

Cool!  Thanks for looking into this, and I've been having
trouble in that department with big alternates files.

> Add a hashmap containing the packfile names as we load them so that
> the average runtime cost of checking for already-loaded packs becomes
> constant.

Btw, would you have time to do a comparison against khash?

AFAIK hashmap predates khash in git; and hashmap was optimized
for removal.   Removals don't seem to be a problem for pack

I'm interested in exploring the removing of hashmap entirely in
favor of khash to keep our codebase smaller and easier-to-learn.
khash shows up more in other projects, and ought to have better

Thanks again.

  reply index

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-27 22:24 Colin Stolley
2019-11-28  0:42 ` Eric Wong [this message]
2019-11-30 17:36   ` hashmap vs khash? " Junio C Hamano
2019-12-02 14:39   ` Jeff King
2019-12-02 17:40 ` SZEDER Gábor
2019-12-02 19:42   ` Jeff King
2019-12-03  6:17     ` Taylor Blau
2019-12-03 15:34       ` Jeff King
2019-12-03 16:04     ` Junio C Hamano
2019-12-03 17:33       ` Colin Stolley
2019-12-03 22:18         ` Jeff King
2019-12-04 18:15           ` Junio C Hamano
2019-12-03 22:17       ` Jeff King
2019-12-04  4:23         ` Jonathan Nieder
2019-12-03  6:19 ` Taylor Blau

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