Re: git-index-pack really does suck..

> 
> 
> On Tue, 3 Apr 2007, Nicolas Pitre wrote:
> >
> > I don't see where that might be.  The only thing that the paranoia check 
> > triggers is:
> > 
> > 	foo = read_sha1_file(blah);
> > 	memcmp(foo with bar);
> > 	free(foo);
> > 
> > So where is that commit ID information actually stored when using 
> > read_sha1_file()?
> 
> I've got the numbers: it uses much more memory when doing even failing 
> lookups, ie:
> 
> 	With --paranoid: 5583 minor pagefaults (21MB)
> 	Without --paranoid: 2957 minor pagefaults (11MB)
> 
> (remember, this was *just* the git pack, not the kernel pack)
> 
> It could be as simple as just the index file itself. That's 11MB for the 
> kernel. Imagine if the index file was 20 times bigger - 200MB of memory 
> paged in with bad access patterns just for unnecessary lookups.

> > Not if you consider that it is performed _while_ receiving (and waiting 
> > for) the pack data over the net in the normal case.
> 
> ..which is why I think it makes sense for "pull" to be paranoid. I just 
> don't think it makes sense to be paranoid *all* the time, since it's 
> clearly expensive.