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From: Jeff King <peff@peff.net>
To: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
Cc: "SZEDER Gábor" <szeder.dev@gmail.com>,
	"Philipp Zabel" <p.zabel@pengutronix.de>,
	git@vger.kernel.org, entwicklung@pengutronix.de
Subject: Re: git slow unless piped to cat
Date: Tue, 27 Aug 2019 14:59:30 -0400	[thread overview]
Message-ID: <20190827185929.GA3150@sigill.intra.peff.net> (raw)
In-Reply-To: <20190827100427.u3a5uvmylm5vddn2@pengutronix.de>

On Tue, Aug 27, 2019 at 12:04:27PM +0200, Uwe Kleine-König wrote:

> 	$ sudo sh -c "echo 3 > /proc/sys/vm/drop_caches"; time env GIT_CONFIG_NOSYSTEM=1 HOME=/nonexistant XDG_CONFIG_HOME=/nonexistant git --no-pager show --no-color --no-decorate v5.2
> 	...
> 
> 	real	0m1.041s
> 	user	0m0.000s
> 	sys	0m0.021s
> 
> 	$ git for-each-ref |wc -l
> 	10013
> 
> So this is indeed the problem.

That's not that many refs. Are they mostly unpacked? Loose refs are
awful on a cold cache, since it's one inode per ref (or worse, since it
has walk the directories, too).

Try:

  find .git/refs -type f | wc -l

to see the loose ones. If there are a lot, try:

  git pack-refs --prune --all

(or just "git gc", which does this).

Modern versions of Git should delete any leftover empty directories
after pruning the loose variants, but I think won't go out of their way
to remove ones they didn't delete from. And those are still expensive to
walk on a cold cache. If it's still slow, try:

  find .git/refs/* -type d | xargs rmdir -v

-Peff

  parent reply	other threads:[~2019-08-27 18:59 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-27  8:15 git slow unless piped to cat Uwe Kleine-König
2019-08-27  8:41 ` SZEDER Gábor
2019-08-27  8:56   ` Uwe Kleine-König
2019-08-27  9:12     ` Philipp Zabel
2019-08-27  9:44       ` SZEDER Gábor
2019-08-27 10:04         ` Uwe Kleine-König
2019-08-27 10:33           ` SZEDER Gábor
2019-08-27 10:56             ` Uwe Kleine-König
2019-08-27 11:28               ` Michal Suchánek
2019-08-27 18:59           ` Jeff King [this message]
2019-08-27 21:32             ` Uwe Kleine-König
2019-08-27 21:38               ` Bryan Turner
2019-08-28 10:24                 ` Uwe Kleine-König

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