From: Jeff King <email@example.com> To: "Ævar Arnfjörð Bjarmason" <firstname.lastname@example.org> Cc: Git Mailing List <email@example.com> Subject: Re: upload-pack is slow with lots of refs Date: Wed, 3 Oct 2012 14:03:24 -0400 [thread overview] Message-ID: <20121003180324.GB27446@sigill.intra.peff.net> (raw) In-Reply-To: <CACBZZX70NTic2WtrXooTg+yBbiFFDAEX_Y-b=W=rAkcYKJ3T2g@mail.gmail.com> On Wed, Oct 03, 2012 at 02:36:00PM +0200, Ævar Arnfjörð Bjarmason wrote: > I'm creating a system where a lot of remotes constantly fetch from a > central repository for deployment purposes, but I've noticed that even > with a remote.$name.fetch configuration to only get certain refs a > "git fetch" will still call git-upload pack which will provide a list > of all references. > > This is being done against a repository with tens of thousands of refs > (it has a tag for each deployment), so it ends up burning a lot of CPU > time on the uploader/receiver side. Where is the CPU being burned? Are your refs packed (that's a huge savings)? What are the refs like? Are they .have refs from an alternates repository, or real refs? Are they pointing to commits or tag objects? What version of git are you using? In the past year or so, I've made several tweaks to speed up large numbers of refs, including: - cff38a5 (receive-pack: eliminate duplicate .have refs, v1.7.6); note that this only helps if they are being pulled in by an alternates repo. And even then, it only helps if they are mostly duplicates; distinct ones are still O(n^2). - 7db8d53 (fetch-pack: avoid quadratic behavior in remove_duplicates) a0de288 (fetch-pack: avoid quadratic loop in filter_refs) Both in v1.7.11. I think there is still a potential quadratic loop in mark_complete() - 90108a2 (upload-pack: avoid parsing tag destinations) 926f1dd (upload-pack: avoid parsing objects during ref advertisement) Both in v1.7.10. Note that tag objects are more expensive to advertise than commits, because we have to load and peel them. Even with those patches, though, I found that it was something like ~2s to advertise 100,000 refs. > Has there been any work on extending the protocol so that the client > tells the server what refs it's interested in? I don't think so. It would be hard to do in a backwards-compatible way, because the advertisement is the first thing the server says, before it has negotiated any capabilities with the client at all. -Peff
next prev parent reply other threads:[~2012-10-03 18:03 UTC|newest] Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top 2012-10-03 12:36 Ævar Arnfjörð Bjarmason 2012-10-03 13:06 ` Nguyen Thai Ngoc Duy 2012-10-03 18:03 ` Jeff King [this message] 2012-10-03 18:53 ` Junio C Hamano 2012-10-03 18:55 ` Jeff King 2012-10-03 19:41 ` Shawn Pearce 2012-10-03 20:13 ` Jeff King 2012-10-04 21:52 ` Sascha Cunz 2012-10-05 0:20 ` Jeff King 2012-10-05 6:24 ` Johannes Sixt 2012-10-05 16:57 ` Shawn Pearce 2012-10-08 15:05 ` Johannes Sixt 2012-10-09 6:46 ` Shawn Pearce 2012-10-09 20:30 ` Johannes Sixt 2012-10-09 20:46 ` Johannes Sixt 2012-10-03 20:16 ` Ævar Arnfjörð Bjarmason 2012-10-03 21:20 ` Jeff King 2012-10-03 22:15 ` Ævar Arnfjörð Bjarmason 2012-10-03 23:15 ` Jeff King 2012-10-03 23:54 ` Ævar Arnfjörð Bjarmason 2012-10-04 7:56 ` [PATCH 0/4] optimizing upload-pack ref peeling Jeff King 2012-10-04 7:58 ` [PATCH 1/4] peel_ref: use faster deref_tag_noverify Jeff King 2012-10-04 18:24 ` Junio C Hamano 2012-10-04 8:00 ` [PATCH 2/4] peel_ref: do not return a null sha1 Jeff King 2012-10-04 18:32 ` Junio C Hamano 2012-10-04 8:02 ` [PATCH 3/4] peel_ref: check object type before loading Jeff King 2012-10-04 19:06 ` Junio C Hamano 2012-10-04 19:41 ` Jeff King 2012-10-04 20:41 ` Junio C Hamano 2012-10-04 21:59 ` Jeff King 2012-10-04 8:03 ` [PATCH 4/4] upload-pack: use peel_ref for ref advertisements Jeff King 2012-10-04 8:04 ` [PATCH 0/4] optimizing upload-pack ref peeling Jeff King 2012-10-04 9:01 ` Ævar Arnfjörð Bjarmason 2012-10-04 12:14 ` Nazri Ramliy 2012-10-03 22:32 ` upload-pack is slow with lots of refs Ævar Arnfjörð Bjarmason 2012-10-03 23:21 ` Jeff King 2012-10-03 23:47 ` Ævar Arnfjörð Bjarmason 2012-10-03 19:13 ` Junio C Hamano
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