linux-kernel - Re: [PATCH v5 0/4] mm/page_reporting: Make page reporting work on arm64 with 64KB page size

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Date:   Fri, 25 Jun 2021 16:17:22 +1000
From:   Gavin Shan <gshan@...hat.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        alexander.duyck@...il.com, david@...hat.com,
        akpm@...ux-foundation.org, anshuman.khandual@....com,
        catalin.marinas@....com, will@...nel.org, shan.gavin@...il.com
Subject: Re: [PATCH v5 0/4] mm/page_reporting: Make page reporting work on
 arm64 with 64KB page size

On 6/25/21 3:58 PM, Michael S. Tsirkin wrote:
> On Fri, Jun 25, 2021 at 12:21:46PM +0800, Gavin Shan wrote:
>> The page reporting threshold is currently equal to @pageblock_order, which
>> is 13 and 512MB on arm64 with 64KB base page size selected. The page
>> reporting won't be triggered if the freeing page can't come up with a free
>> area like that huge. The condition is hard to be met, especially when the
>> system memory becomes fragmented.
>>
>> This series intends to solve the issue by having page reporting threshold
>> as 5 (2MB) on arm64 with 64KB base page size. The patches are organized as:
>>
>>     PATCH[1/4] Fix some coding style in __page_reporting_request().
>>     PATCH[2/4] Represents page reporting order with variable so that it can
>>                be exported as module parameter.
>>     PATCH[3/4] Allows the device driver (e.g. virtio_balloon) to specify
>>                the page reporting order when the device info is registered.
>>     PATCH[4/4] Specifies the page reporting order to 5, corresponding to
>>                2MB in size on ARM64 when 64KB base page size is used.
> 
> I sent comments on v4. They still apply I think. Want me to repeat them
> here?
> 

Thanks for your comments, Michael. I've replied to your comments
through v4. There are some future work as Alex and David pointed
out before: In order to remove the hack in virtio-memballoon, the
VMM needs to report the page reporting order. I will keep working
on this when I have spare time.

Thanks,
Gavin

>> Changelog
>> =========
>> v5:
>>     * Restore @page_reporting_order to @pageblock_order when
>>       device is registered in PATCH[2/4] to keep "git bisect"
>>       friendly at least.                                           (Alex)
>> v4:
>>     * Set @page_reporting_order to MAX_ORDER. Its value is
>>       specified by the driver or falls back to @pageblock_order
>>       when page reporting device is registered.                    (Alex)
>>     * Include "module.h" in page_reporting.c                       (Andrew)
>> v3:
>>     * Avoid overhead introduced by function all                    (Alex)
>>     * Export page reporting order as module parameter              (Gavin)
>> v2:
>>     * Rewrite the patches as Alex suggested                        (Alex)
>>
>> Gavin Shan (4):
>>    mm/page_reporting: Fix code style in __page_reporting_request()
>>    mm/page_reporting: Export reporting order as module parameter
>>    mm/page_reporting: Allow driver to specify reporting
>>    virtio_balloon: Specify page reporting order if needed
>>
>>   .../admin-guide/kernel-parameters.txt         |  6 +++++
>>   drivers/virtio/virtio_balloon.c               | 17 ++++++++++++++
>>   include/linux/page_reporting.h                |  3 +++
>>   mm/page_reporting.c                           | 22 +++++++++++++++----
>>   mm/page_reporting.h                           |  5 ++---
>>   5 files changed, 46 insertions(+), 7 deletions(-)
>>
>> -- 
>> 2.23.0
>