Re: [PATCH 0/4] enable migration of driver pages

[Konstantin Khlebnikov]

On Mon, Jul 13, 2015 at 11:35 AM, Gioh Kim <gioh.kim@xxxxxxx> wrote:
> From: Gioh Kim <gurugio@xxxxxxxxxxx>
>
> Hello,
>
> This series try to enable migration of non-LRU pages, such as driver's page.
>
> My ARM-based platform occured severe fragmentation problem after long-term
> (several days) test. Sometimes even order-3 page allocation failed. It has
> memory size 512MB ~ 1024MB. 30% ~ 40% memory is consumed for graphic processing
> and 20~30 memory is reserved for zram.
>
> I found that many pages of GPU driver and zram are non-movable pages. So I
> reported Minchan Kim, the maintainer of zram, and he made the internal
> compaction logic of zram. And I made the internal compaction of GPU driver.
>
> They reduced some fragmentation but they are not enough effective.
> They are activated by its own interface, /sys, so they are not cooperative
> with kernel compaction. If there is too much fragmentation and kernel starts
> to compaction, zram and GPU driver cannot work with the kernel compaction.
>
> So I thought there needs a interface to combine driver and kernel compaction.
> This patch adds a generic isolate/migrate/putback callbacks for page
> address-space and a new interface to create anon-inode to manage
> address_space_operation. The zram and GPU, and any other modules can create
> anon_inode and register its own migration method. The kernel compaction can
> call the registered migration when it does compaction.
>
> My GPU driver source is not in-kernel driver so that I apply the interface
> into balloon driver. The balloon driver is already merged
> into the kernel compaction as a corner-case. This patch have the balloon
> driver migration be called by the generic interface.
>
>
> This patch set combines 4 patches.
>
> 1. patch 1/4: get inode from anon_inodes
> This patch adds new interface to create inode from anon_inodes.
>
> 2. patch 2/4: framework to isolate/migrate/putback page
> Add isolatepage, putbackpage into address_space_operations
> and wrapper function to call them.
>
> 3. patch 3/4: apply the framework into balloon driver
> The balloon driver is applied into the framework. It gets a inode
> from anon_inodes and register operations in the inode.
> The kernel compaction calls generic interfaces, not balloon
> driver interfaces.
> Any other drivers can register operations via inode like this
> to migrate it's pages.
>
> 4. patch 4/4: remove direct calling of migration of driver pages
> Non-lru pages are also migrated with lru pages by move_to_new_page().

The whole patchset looks good.

Reviewed-by: Konstantin Khlebnikov <koct9i@xxxxxxxxx>

>
> This patch set is tested:
> - turn on Ubuntu 14.04 with 1G memory on qemu.
> - do kernel building
> - after several seconds check more than 512MB is used with free command
> - command "balloon 512" in qemu monitor
> - check hundreds MB of pages are migrated

Another simple test is several instances of
tools/testing/selftests/vm/transhuge-stress.c
runnng in parallel with balloon inflating/deflating.
(transparent huge pages must be enabled of course)
That catched a lot of races in ballooning code.

>
> My thanks to Konstantin Khlebnikov for his reviews of the RFC patch set.
> Most of the changes were based on his feedback.
>
> This patch-set is based on v4.1
>
>
> Gioh Kim (4):
>   fs/anon_inodes: new interface to create new inode
>   mm/compaction: enable mobile-page migration
>   mm/balloon: apply mobile page migratable into balloon
>   mm: remove direct calling of migration
>
>  drivers/virtio/virtio_balloon.c        |  3 ++
>  fs/anon_inodes.c                       |  6 +++
>  fs/proc/page.c                         |  3 ++
>  include/linux/anon_inodes.h            |  1 +
>  include/linux/balloon_compaction.h     | 15 +++++--
>  include/linux/compaction.h             | 80 ++++++++++++++++++++++++++++++++++
>  include/linux/fs.h                     |  2 +
>  include/linux/page-flags.h             | 19 ++++++++
>  include/uapi/linux/kernel-page-flags.h |  1 +
>  mm/balloon_compaction.c                | 72 ++++++++++--------------------
>  mm/compaction.c                        |  8 ++--
>  mm/migrate.c                           | 24 +++-------
>  12 files changed, 160 insertions(+), 74 deletions(-)
>
> --
> 2.1.4
>
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