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 01:58:51 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Gavin Shan <gshan@...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 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?

> 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