Re: git grep performance regression

Ross Lagerwall [off-list ref] writes:

I have noticed a performance regression in git grep between v1.8.1 and
v1.8.1.1:

On the kernel tree:
For git 1.8.1:
$ time git grep foodsgsg

real   0m0.158s
user   0m0.290s
sys    0m0.207s

For git 1.8.1.1:
$ time /tmp/g/bin/git grep foodsgsg

real   0m0.501s
user   0m0.707s
sys    0m0.493s


A bisect seems to indicate that it was introduced by 94bc67:
commit 94bc671a1f2e8610de475c2494d2763355a99f65
Author: Jean-Noël AVILA [off-list ref]
Date:   Sat Dec 8 21:04:39 2012 +0100

    Add directory pattern matching to attributes
    
    The manpage of gitattributes says: "The rules how the pattern
    matches paths are the same as in .gitignore files" and the gitignore
    pattern matching has a pattern ending with / for directory matching.
    
    This rule is specifically relevant for the 'export-ignore' rule used
    for git archive.
    
    Signed-off-by: Jean-Noel Avila [off-list ref]
    Signed-off-by: Junio C Hamano [off-list ref]

Hmph, that looks really bad, especially given that in the normal
codepath like "git grep", we would never care about directories (the
attributes are normally applied to real paths with contents, and the
use by archive is an anomaly) and the implementation should be done
in a way not to impose such excess and useless overhead.

We may end up reverting that patch for the time being X-<.

Jean-Noël, ideas?