Git Mailing List Archive on lore.kernel.org
 help / color / Atom feed
From: Eric Wong <e@80x24.org>
To: Colin Stolley <cstolley@runbox.com>
Cc: git@vger.kernel.org
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: <20191127222453.GA3765@owl.colinstolley.com>

Colin Stolley <cstolley@runbox.com> 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
loading.

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
cache-locality.

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

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20191128004202.GA25910@dcvr \
    --to=e@80x24.org \
    --cc=cstolley@runbox.com \
    --cc=git@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Git Mailing List Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/git/0 git/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 git git/ https://lore.kernel.org/git \
		git@vger.kernel.org
	public-inbox-index git

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.git


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git