Re: RAM consumption when working with the gcc repo

["Jon Smirl" <jonsmirl@gmail.com>]

On 12/7/07, Nicolas Pitre <nico@cam.org> wrote:
> On Fri, 7 Dec 2007, david@lang.hm wrote:
>
> > On Fri, 7 Dec 2007, Jon Smirl wrote:
> >
> > > I noticed two things when doing a repack of the gcc repo. First is
> > > that the git process is getting to be way too big. Turning off the
> > > delta caches had minimal impact. Why does the process still grow to
> > > 4.8GB?
> > >
> > > Putting this in perspective, this is a 4.8GB process constructing a
> > > 330MB file. Something isn't right. Memory leak or inefficient data
> > > structure?
> >
> > keep in mind that that 330MB file is _very_ heavily compressed. the simple
> > zlib compression is probably getting you 10:1 or 20:1 compression and the
> > delta compression is a significant multiplier on top of that.
>
> Doesn't matter.  Something is indeed fishy.

I didn't have any problem repacking Mozilla and it ends up as a 450MB
pack file with 1.5M entries.  So something has changed. With Mozilla I
had a 3GB machine, and now I can't finish a 330MB pack on a 4GB
machine. I don't recall the Mozilla process ever exceeding 2GB.


>
> The bulk of pack-objects memory consumption can be estimated as follows:
>
> 1M objects * sizeof(struct object_entry) ~= 100MB
> 256 window entries with data (assuming a big 1MB per entry) = 256MB
> Delta result caching was disabled therefore 0MB
> read-side delta cache limited to 16MB
>
> So the purely ram allocation might get to roughly 400MB.
>
> Then add the pack and index map, which, depending on the original pack
> size,
> might be 2GB.
>
> So we're pessimistically talking of about 2.5GB of virtual space.
>
> The other 2.3GB is hard to explain.
>
>
> Nicolas
>


-- 
Jon Smirl
jonsmirl@gmail.com