Re: [PATCH v3 00/16] Support non-lru page migration

From: Andrew Morton
Date: Wed Mar 30 2016 - 19:11:48 EST

On Wed, 30 Mar 2016 16:11:59 +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 failed to fork easily.
> The problem was fragmentation caused by zram and GPU driver
> pages. Their pages cannot be migrated so compaction cannot
> work well, either so reclaimer ends up shrinking all of working
> set pages. It made system very slow and even to fail to fork
> easily.
> Other pain point is that they cannot work with CMA.
> Most of CMA memory space could be idle(ie, it could be used
> for movable pages unless driver is using) but if driver(i.e.,
> zram) cannot migrate his page, that memory space could be
> wasted. In our product which has big CMA memory, it reclaims
> zones too exccessively although there are lots of free space
> in CMA so system was very slow easily.
> To solve these problem, this patch try to add facility to
> migrate non-lru pages via introducing new friend functions
> of migratepage in address_space_operation and new page flags.
> (isolate_page, putback_page)
> (PG_movable, PG_isolated)
> For details, please read description in
> "mm/compaction: support non-lru movable page migration".

OK, I grabbed all these.

I wonder about testing coverage during the -next period. How many
people are likely to exercise these code paths in a serious way before
it all hits mainline?