Re: [Lsf-pc] [LSF/MM ATTEND] 2016: Requests to attend MM-summit

[Jan Kara <jack@suse.cz>]

On Fri 22-01-16 20:17:07, Balbir Singh wrote:
> On Fri, 22 Jan 2016 10:11:12 +0530
> "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> wrote:
> 
> > Hi,
> > 
> > I would like to attend LSF/MM this year (2016).
> > 
> > My main interest is in MM related topics although I am also interested
> > in the btrfs status discussion (particularly related to subpage size block
> > size topic), if we are having one. Most of my recent work in the kernel is
> > related to adding ppc64 support for different MM features. My current focus
> > is on adding Linux support for the new radix MMU model of Power9.
> > 
> > Topics of interest include:
> > 
> > * CMA allocator issues:
> >   (1) order zero allocation failures:
> >       We are observing order zero non-movable allocation failures in kernel
> > with CMA configured. We don't start a reclaim because our free memory check
> > does not consider free_cma. Hence the reclaim code assume we have enough free
> > pages. Joonsoo Kim tried to fix this with his ZOME_CMA patches. I would
> > like to discuss the challenges in getting this merged upstream.
> > https://lkml.org/lkml/2015/2/12/95 (ZONE_CMA)
> > 
> > Others needed for the discussion:
> > Joonsoo Kim <iamjoonsoo.kim@lge.com>
> > 
> >   (2) CMA allocation failures due to pinned pages in the region:
> >       We allow only movable allocation from the CMA region to enable us
> > to migrate those pages later when we get a CMA allocation request. But
> > if we pin those movable pages, we will fail the migration which can result
> > in CMA allocation failure. One such report can be found here.
> > http://article.gmane.org/gmane.linux.kernel.mm/136738
> > 
> > Peter Zijlstra's VM_PINNED patch series should help in fixing the issue. I would
> > like to discuss what needs to be done to get this patch series merged upstream
> > https://lkml.org/lkml/2014/5/26/345 (VM_PINNED)
> > 
> > Others needed for the discussion:
> > Peter Zijlstra <peterz@infradead.org>
> 
> +1
> 
> I agree CMA design is a concern. I also noticed that today all CMA pages come
> from one node. On a NUMA box you'll see cross traffic going to that region -
> although from kernel only text. It should be discussed at the summit and Aneesh
> would be a good representative

I'm not really an mm guy but CMA has been discussed already last year, and
I think even the year before... Are we moving somewhere? So if this is
about hashing out what blocks VM_PINNED series (I think it may be just a
lack of Peter's persistence in pushing it ;) then that looks like a
sensible goal. Some other CMA architecture discussions need IMHO a more
concrete proposals...

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

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