Re: performance problem: "git commit filename"

From: Kristian Høgsberg <krh@redhat.com>
Date: Jan 14, 2008, 23:46 UTC
Message-ID: <1200354379.488.17.camel@gaara.boston.redhat.com>
In-Reply-To: <alpine.LFD.1.00.0801121949180.2806@woody.linux-foundation.org>

On Sat, 2008-01-12 at 20:04 -0800, Linus Torvalds wrote:

Show 15 quoted lines

> It makes builtin-commit.c use the same logic that "git read-tree -i -m" 
> does (which is what the old shell script did), and it seems to pass the 
> test-suite, and it looks pretty obvious.
> 
> It also brings down the number of open/mmap/munmap/close calls to where it 
> should be, although it still does *way* too many "lstat()" operations (ie 
> it does 4*lstat for each file in the index - one more than the 
> non-filename one does).
> 
> With that fixed, performance is also roughly where it should be (ie the 
> 17-18s for the cold-cache case), because it no longer needs to rehash all 
> the files!
> 
> HOWEVER. This was just a quick hack, and while it all looks sane, this is 
> some damn core code. Somebody else should double- and triple-check this.

I took a look too, and it looks to me like the it's the exact same code path in builtin-read-tree.c that the old

        git read-tree --index-output="$TMP_INDEX" -i -m HEAD

part of the shell script would trigger. So yes, this look like the right fix to me.

Signed-off-by: Kristian Høgsberg <krh@redhat.com>