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From: Junio C Hamano <gitster@pobox.com>
To: Eric Wong <e@80x24.org>
Cc: Lars Schneider <larsxschneider@gmail.com>,
	Git Mailing List <git@vger.kernel.org>,
	tboegi@web.de, Johannes.Schindelin@gmx.de
Subject: Re: [PATCH v1 2/2] read-cache: make sure file handles are not inherited by child processes
Date: Wed, 07 Sep 2016 11:23:39 -0700	[thread overview]
Message-ID: <xmqqtwdrmuvo.fsf@gitster.mtv.corp.google.com> (raw)
In-Reply-To: <20160907181036.GA14931@starla> (Eric Wong's message of "Wed, 7 Sep 2016 18:10:36 +0000")

Eric Wong <e@80x24.org> writes:

> We probably should be using O_NOATIME for all O_RDONLY cases
> to get the last bit of performance out (especially since
> non-modern-Linux systems probably still lack relatime).

No, please do not go there.

The user can read from a file in a working tree using "less",
"grep", etc., and they all update the atime, so should "git grep".
We do not use atime ourselves on these files but we should let
outside tools rely on the validity of atime (e.g. "what are the
files that were looked at yesterday?").

If you grep for noatime in our current codebase, you'd notice that
we use it only for files in objects/ hierarchy, and that makes very
good sense.  These files are what we create for our _sole_ use and
no other tools can peek at them and expect to get any useful
information out of them (we hear from time to time that virus
scanners leaving open file descriptors on them causing trouble, but
that is an example of a useless access), and that makes a file in
objects/ hierarchy a fair game for noatime optimization.

  reply	other threads:[~2016-09-07 18:23 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-09-05 21:11 [PATCH v1 0/2] Use CLOEXEC to avoid fd leaks larsxschneider
2016-09-05 21:11 ` [PATCH v1 1/2] sha1_file: open window into packfiles with CLOEXEC larsxschneider
2016-09-05 22:27   ` Eric Wong
2016-09-06  9:36     ` Jakub Narębski
2016-09-06 11:38     ` Johannes Schindelin
2016-09-07 13:20       ` Lars Schneider
2016-09-07 18:17         ` Eric Wong
2016-09-05 21:11 ` [PATCH v1 2/2] read-cache: make sure file handles are not inherited by child processes larsxschneider
2016-09-06 11:41   ` Johannes Schindelin
2016-09-06 21:06   ` Eric Wong
2016-09-07 13:39     ` Lars Schneider
2016-09-07 18:10       ` Eric Wong
2016-09-07 18:23         ` Junio C Hamano [this message]
2016-09-08  5:57           ` Lars Schneider
2016-09-08 17:37             ` Junio C Hamano

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