Re: [patch] vmfixes-2.4.0-test9-B2 - fixing deadlocks

Andrea Arcangeli
2000-09-26T14:05:54Z

On Tue, Sep 26, 2000 at 08:54:23AM +0200, Christoph Rohland wrote:
> "Stephen C. Tweedie" <sct@redhat.com> writes:
>
> > Hi,
> >
> > On Mon, Sep 25, 2000 at 09:32:42PM +0200, Andrea Arcangeli wrote:
> >
> > > Having shrink_mmap that browse the mapped page cache is useless
> > > as having shrink_mmap browsing kernel memory and anonymous pages
> > > as it does in 2.2.x as far I can tell. It's an algorithm
> > > complexity problem and it will waste lots of CPU.
> >
> > It's a compromise between CPU cost and Getting It Right. Ignoring the
> > mmap is not a good solution either.
> >
> > > Now think this simple real life example. A 2G RAM machine running
> > > an executable image of 1.5G, 300M in shm and 200M in cache.
>
> Hey that's ridiculous: 1.5G executable image and 300M shm? Take it
> vice-versa and you are approaching real life.

Could you tell me what's wrong in having an app with a 1.5G mapped executable
(or a tiny executable but with a 1.5G shared/private file mapping if you
prefer), 300M of shm (or 300M of anonymous memory if you prefer) and 200M as
filesystem cache?

The application have a misc I/O load that in some part will run out
of the working set, what's wrong with this?

What's ridiculous? Please elaborate.

To emulate that workload we only need to mmap(1.5G, MAP_PRIVATE or MAP_SHARED),
fault into it, and run bonnie.

Andrea