From: Johannes Schindelin <Johannes.Schindelin@gmx.de>
To: Junio C Hamano <gitster@pobox.com>
Cc: "Gumbel, Matthew K" <matthew.k.gumbel@intel.com>,
"git@vger.kernel.org" <git@vger.kernel.org>
Subject: Re: [PATCH] commit: Optimize number of lstat() calls
Date: Sat, 4 Feb 2017 01:35:56 +0100 (CET) [thread overview]
Message-ID: <alpine.DEB.2.20.1702040129430.3496@virtualbox> (raw)
In-Reply-To: <xmqqwpd678lx.fsf@gitster.mtv.corp.google.com>
Hi Junio,
On Fri, 3 Feb 2017, Junio C Hamano wrote:
> Aside from whitespace breakage, I think we should never skip the
> refreshing of the real index that is left after "git commit"
> finishes.
>
> Between these two calls to refresh_cache(), the one that writes out
> a temporary index that contains the contents of HEAD plus the
> contents of the working tree for the specified paths may be fine
> without refreshing, unless somebody else (like the pre-commit hook)
> looks at it. But the other one refreshes the real index file that
> will be used after "git commit" returns the control. Users and
> scripts that run "git commit" inside expect that the entries in the
> resulting index are refreshed after "git commit" returns, and I do
> not think of a safe way to optimizing it out; unlike the other one,
> to which we can say "as long as there is no pre-commit hook, nobody
> will look at it after we are done", there does not an easy-to-check
> set of conditions that we can use to decide when it is safe to skip
> refreshing.
>
> Besides, leaving the main index not refreshed would mean the user
> has to pay the refreshing cost when s/he runs other commands "git
> diff", "git status", etc. after "git commit" for the first time;
> so...
I am not sure... when you run `git diff` and `git status`, the index is
refreshed *anyway*, so with the patch under discussion we would save one
round of lstat() calls, for the same effect.
I could imagine that there is a third option we should consider, too: only
lstat() and update the paths that match the pathspec(s) provided on the
command line (this is the semantic meaning of the --only option, after
all: "I am only interested in these paths as far as this commit is
concerned"). What do you think?
Ciao,
Johannes
next prev parent reply other threads:[~2017-02-04 7:15 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-03 23:22 [PATCH] commit: Optimize number of lstat() calls Gumbel, Matthew K
2017-02-03 23:38 ` Junio C Hamano
2017-02-04 6:50 ` Junio C Hamano
2017-02-04 0:35 ` Johannes Schindelin [this message]
2017-02-04 7:23 ` Junio C Hamano
2017-02-04 10:42 ` Johannes Schindelin
Reply instructions:
You may reply publicly 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
List information: http://vger.kernel.org/majordomo-info.html
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=alpine.DEB.2.20.1702040129430.3496@virtualbox \
--to=johannes.schindelin@gmx.de \
--cc=git@vger.kernel.org \
--cc=gitster@pobox.com \
--cc=matthew.k.gumbel@intel.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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://80x24.org/mirrors/git.git
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).