Re: Excessive mmap [was Git server eats all memory]

[Duy Nguyen <pclouds@gmail.com>]

On Tue, Jun 19, 2018 at 10:27 PM Ivan Kanis
<expire-by-2010-08-14@kanis.fr> wrote:
>
> Dmitry Potapov <dpotapov@gmail.com> wrote:
>
> > On Fri, Aug 06, 2010 at 07:23:17PM +0200, Ivan Kanis wrote:
> >>
> >> I expected the malloc to take 4G but was surprised it didn't. It seems
> >> to be mmap taking all the memory. I am not familiar with that function,
> >> it looks like it's mapping memory to a file... Is it reasonable to mmap
> >> so much memory?
> >
> > AFAIK, Git does not need to mmap the whole pack to memory, but it
> > is more efficient to mmap the whole pack wherever possible, because
> > it has a completely random access, so if you store only one sliding
> > window, you will have to re-read it many times. Besides, mmap size
> > does not mean that so much physical memory is used. Pages should
> > be loaded when they are necessary, and if you have more than one
> > client cloning the same repo, this memory should be shared by them.
>
> I have clone identical repositories and the system starts to swap. I
> think it shows that cloning two repository doesn't share mmap.

I doubt it (assuming you're on linux). If you suspect this, configure
core.packedGitWindowSize to reduce the mmap size. There are lots of
other things in a cloning process that do not share (is this client or
server btw?) and things could add up.
--
Duy