From: Joachim B Haga <cjhaga@fys.uio.no>
Date: Sat, 01 Dec 2007 11:36:04 GMT
Subject: Re: Some git performance measurements..
Message-ID: <85abou8x5n.fsf@lupus.ig3.net>
In-Reply-To: <alpine.LFD.0.9999.0711281852160.8458@woody.linux-foundation.org>

Linus Torvalds <torvalds@linux-foundation.org> writes:

> The pack-files (both index and data) are accessed somewhat randomly, but 
> there is still enough locality that doing read-ahead and clustering really 
> does help.

They are dense enough that slurping them in whole is 20% faster, at 
least here. And much less noisy! These are both cache-cold tests.

$ time git read-tree -m -u HEAD HEAD

real    0m9.255s
user    0m0.832s
sys     0m0.196s

$ time (cat .git/objects/pack/* .git/index >/dev/null; git read-tree -m -u HEAD HEAD)

real    0m7.141s
user    0m0.936s
sys     0m1.912s


Now, I don't know how useful this is since git doesn't know if the
data are cached. Is it perhaps possible to give a hint to the
readahead logic that it should try to read as far as possible?


-j.