From mboxrd@z Thu Jan  1 00:00:00 1970
From: Joachim B Haga <cjhaga@fys.uio.no>
Subject: Re: Some git performance measurements..
Date: Sat, 01 Dec 2007 12:36:04 +0100
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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.