Re: MM deadlock [was: Re: arca-vm-8...]

Rik van Riel
1999-01-25T15:24:02Z

On Mon, 25 Jan 1999, Alan Cox wrote:

> > If I understand well the problem is get more than 1<<maxorder contiguos
> > phys pages in RAM. I think it should not too difficult to do a dirty hack
>
> Yep. We are talking about 2->4Mb sized chunks. We are also talking about
> chunks that are allocated rarely

> > alternate __get_big_pages that does some try to get many mem-areas of the
> > maximal order contigous. Maybe it will not able to give you such contiguos
> > memory (due mem fragmentation) but if it's possible it will give back it
> > to you (_slowly_).
>
> That fact we effectively "poison" the various blocks of memory
> with locked down kernel objects is what makes this so tricky. It
> really needs some back pressure applied so that kernel allocations
> come from a limited number of maxorder blocks, at least except
> under exceptional circumstances.

We need a different memory allocator for that. Maybe it's
time to dig up my zone allocator proposal (on my home page)
and adapt it to something working.

Unfortunately I don't have the time to do that, so I'll
leave the job to Alan or Stephen (who should have the time
since they're with Red Hat)...

> I think its too tricky for 2.2 even as a later retrofit

Once the allocator is ready and stabilized, we might be
able to retrofit it to 2.2. It's just a single module
we need to touch...

cheers,

Rik -- If a Microsoft product fails, who do you sue?
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