On Wed, 27 Apr 2016 16:48:13 +0900 Minchan Kim [off-list ref] 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.

To solve these problem, this patch tries to add facility to migrate
non-lru pages via introducing new functions and page flags to help
migration.

I'm seeing some rejects here against Mel's changes and our patch
bandwidth is getting waaay way ahead of our review bandwidth.  So I
think I'll loadshed this patchset at this time, sorry.