Re: [PATCH v7 00/12] Support non-lru page migration

[Minchan Kim]

On Wed, Jun 01, 2016 at 02:41:51PM -0700, Andrew Morton wrote:
> On Wed,  1 Jun 2016 08:21:09 +0900 Minchan Kim <minchan@xxxxxxxxxx> wrote:
> 
> > Recently, I got many reports about perfermance degradation in embedded
> > system(Android mobile phone, webOS TV and so on) and easy fork fail.
> > 
> > The problem was fragmentation caused by zram and GPU driver mainly.
> > With memory pressure, their pages were spread out all of pageblock and
> > it cannot be migrated with current compaction algorithm which supports
> > only LRU pages. In the end, compaction cannot work well so reclaimer
> > shrinks all of working set pages. It made system very slow and even to
> > fail to fork easily which requires order-[2 or 3] allocations.
> > 
> > Other pain point is that they cannot use CMA memory space so when OOM
> > kill happens, I can see many free pages in CMA area, which is not
> > memory efficient. In our product which has big CMA memory, it reclaims
> > zones too exccessively to allocate GPU and zram page although there are
> > lots of free space in CMA so system becomes very slow easily.
> 
> But this isn't presently implemented for GPU drivers or for CMA, yes?

For GPU driver, Gioh implemented but it was proprietary so couldn't
contribute.

For CMA, [zram: use __GFP_MOVABLE for memory allocation] added __GFP_MOVABLE
for zsmalloc page allocation so it can use CMA area automatically now.

> 
> What's the story there?