Git Mailing List Archive on lore.kernel.org
 help / color / Atom feed
From: Jeff King <peff@peff.net>
To: "SZEDER Gábor" <szeder.dev@gmail.com>
Cc: Colin Stolley <cstolley@runbox.com>, git@vger.kernel.org
Subject: Re: [PATCH] packfile.c: speed up loading lots of packfiles.
Date: Mon, 2 Dec 2019 14:42:31 -0500
Message-ID: <20191202194231.GA10707@sigill.intra.peff.net> (raw)
In-Reply-To: <20191202174035.GJ23183@szeder.dev>

On Mon, Dec 02, 2019 at 06:40:35PM +0100, SZEDER Gábor 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.
> > 
> > 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.
> [...]
> This patch break test 'gc --keep-largest-pack' in 't6500-gc.sh' when
> run with GIT_TEST_MULTI_PACK_INDEX=1, because there is a duplicate
> entry in '.git/objects/info/packs':

Good catch. The issue is that we only add entries to the hashmap in
prepare_packed_git(), but they may be added to the pack list by other
callers of install_packed_git(). It probably makes sense to just push
the hashmap maintenance down into that function, like below. That
requires an extra strhash() when inserting a new pack, but I don't think
that's a big deal.

diff --git a/packfile.c b/packfile.c
index 253559fa87..f0dc63e92f 100644
--- a/packfile.c
+++ b/packfile.c
@@ -757,6 +757,9 @@ void install_packed_git(struct repository *r, struct packed_git *pack)
 
 	pack->next = r->objects->packed_git;
 	r->objects->packed_git = pack;
+
+	hashmap_entry_init(&pack->packmap_ent, strhash(pack->pack_name));
+	hashmap_add(&r->objects->pack_map, &pack->packmap_ent);
 }
 
 void (*report_garbage)(unsigned seen_bits, const char *path);
@@ -864,11 +867,8 @@ static void prepare_pack(const char *full_name, size_t full_name_len,
 		/* Don't reopen a pack we already have. */
 		if (!hashmap_get(&data->r->objects->pack_map, &hent, pack_name)) {
 			p = add_packed_git(full_name, full_name_len, data->local);
-			if (p) {
-				hashmap_entry_init(&p->packmap_ent, hash);
-				hashmap_add(&data->r->objects->pack_map, &p->packmap_ent);
+			if (p)
 				install_packed_git(data->r, p);
-			}
 		}
 		free(pack_name);
 	}

-Peff

  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 ` hashmap vs khash? " Eric Wong
2019-11-30 17:36   ` Junio C Hamano
2019-12-02 14:39   ` Jeff King
2019-12-02 17:40 ` SZEDER Gábor
2019-12-02 19:42   ` Jeff King [this message]
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=20191202194231.GA10707@sigill.intra.peff.net \
    --to=peff@peff.net \
    --cc=cstolley@runbox.com \
    --cc=git@vger.kernel.org \
    --cc=szeder.dev@gmail.com \
    /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