[linux-3.10.17] Could not allocate memory from free CMA areas

[Joonsoo Kim]

On Tue, Aug 05, 2014 at 08:24:50PM +0530, Pintu Kumar wrote:
> Hello,
> 
> > From: iamjoonsoo.kim at lge.com
> > To: pintu_agarwal at yahoo.com; linux-mm at kvack.org; linux-arm-kernel at lists.infradead.org; linaro-mm-sig at lists.linaro.org; ritesh.list at gmail.com
> > CC: pintu.k at outlook.com; pintu.k at samsung.com; vishu_1385 at yahoo.com; m.szyprowski at samsung.com; mina86 at mina86.com; ngupta at vflare.org; iqbalblr at gmail.com
> > Subject: RE: [linux-3.10.17] Could not allocate memory from free CMA areas
> > Date: Mon, 4 Aug 2014 16:11:00 +0900
> > 
> >> Dear Joonsoo,
> >> 
> >> I tried your changes which are present at the below link. 
> >> https://github.com/JoonsooKim/linux/tree/cma-fix-up-v3.0-next-20140625
> >> But unfortunately for me it did not help much. 
> >> After running various apps that uses ION nonmovable memory, it fails to allocate memory after some time. When I see the pagetypeinfo shows lots of CMA pages available and non-movable were very less and thus nonmovable allocation were failing.
> > 
> > Okay. CMA pages cannot be used for nonmovable memory, so it can fail in above case.
> > 
> >> However I noticed the failure was little delayed.
> > 
> > It is good sign. I guess that there is movable/CMA ratio problem.
> > My patchset uses free CMA pages in certain ratio to free movable page consumption.
> > If your system doesn't use movable page sufficiently, free CMA pages cannot
> > be used fully. Could you test with following workaround?
> > 
> > +       if (normal> cma) {
> > +               zone->max_try_normal = pageblock_nr_pages;
> > +               zone->max_try_cma = pageblock_nr_pages;
> > +       } else {
> > +               zone->max_try_normal = pageblock_nr_pages;
> > +               zone->max_try_cma = pageblock_nr_pages;
> > +       }
> 
> I applied these changes but still the allocations are failing because there are no non-movable memory left in the system.

Hello,

kswapd doesn't work?
Please let me know your problem in detail.

> With the changes I noticed that nr_cma_free sometimes becomes almost zero.
> But in our case Display/Xorg needs to have atleast 8MB of CMA (contiguous) memory of order-8 and order-4 type.
> CMA:56MB is shared across display,camera,video etc.

Used CMA pages will be released automatically when your Display/Xorg
request them. So you don't need to worry about empty of free CMA pages.

> 
> I think the previous changes are slightly better.
> 
> My concern is that whether I am applying all you changes or missing some thing.
> I saw that your kernel version is based on next-20140625 but my kernel version is 3.10.17.
> And till now I applied only the below changes:
> https://github.com/JoonsooKim/linux/commit/33a0416b3ac1cd7c88e6b35ee61b4a81a7a14afc 
> 
> But I haven't applied this:
> https://github.com/JoonsooKim/linux/commit/166b4186d101b190cf50195d841e2189f2743649
> (CMA: always treat free cma pages as non-free on watermark checking)

This patch is somewhat related to your failure of non-movable memory
allocation. It is simple so that you can easily backport.

> These changes have other dependencies which is not present in my kernel version.
> Like inclusion of ALLOC_FAIR and area->nr_cma_free.
> Please let me know if these changes are also important for "aggressive alloc changes..."
> 
> If possible please send me all the patches related to "aggressive cma.." so that I can conclude on my experiment.

Until now, that's all. :)

Thanks.