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

[Gioh Kim]

2015-07-13 ìí 6:24ì Konstantin Khlebnikov ì(ê) ì ê:
> 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.

Great!
I'll do it and inform you the result in this week.
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