Re: Public repro case! Re: [PATCH/RFC] Allow writing loose objects that are corrupted in a pack file

On Wed, 2009-01-07 at 16:48 -0800, Linus Torvalds wrote:

On Wed, 7 Jan 2009, R. Tyler Ballance wrote:

quoted

My most esteemed colleague (Ken aka kb) who pointed out the memory issue
was on the right path (I think), and I have a reproduction case you can
try with your very own Linux kernel tree!

WOO!

I set ulimit -v really low (150M), and the operations I made got an
mmap(2) fatal error, but there is a sweet spot that I found, see the
transcript below.

This is indeed the packfile mapping. The sweet spot you found depends on 
how big the biggest two pack-files are, I do believe.

And if you do that

	[core]
		packedgitwindowsize = 64M

I think you'll find that it works. Of course, with a _really_ low ulimit, 
you'd need to make it even smaller, but at some point you start hitting 
other problems than the pack-file limits, ie just the simple fact that git 
wants and expects you to have a certain amount of memory available ;)

Can you cnfirm that your "reproducible" case starts working with that 
addition to your ~/.gitconfig? If so, the solution is pretty simple: we 
should just lower the default pack windowsize.

This certainly corrected the issue, is there some magic
packedgitwindowsize that i should be looking at my own repository (our
internal one) in order to prevent the issue from occurring? 

Looking into .git/objects/pack, I think the two biggest pack files are
3.5G and 177MBG respectively :-!


Cheers
-- 
-R. Tyler Ballance
Slide, Inc.