linux-kernel - Re: [PATCH 0/2] mm: Use pte marker for swapin errors

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Message-ID: <87h6zkepog.fsf@yhuang6-desk2.ccr.corp.intel.com>
Date:   Mon, 31 Oct 2022 09:40:15 +0800
From:   "Huang, Ying" <ying.huang@...el.com>
To:     Peter Xu <peterx@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Miaohe Lin <linmiaohe@...wei.com>,
        David Hildenbrand <david@...hat.com>,
        HORIGUCHI NAOYA <naoya.horiguchi@....com>,
        Andrea Arcangeli <aarcange@...hat.com>
Subject: Re: [PATCH 0/2] mm: Use pte marker for swapin errors

Peter Xu <peterx@...hat.com> writes:

> rfc->v1:
> - Rename SWAP_ERROR -> SWAPIN_ERROR [David, Miaohe]
> - Added r-bs for Ying and Miaohe
>
> Hi,
>
> This series uses the pte marker to replace the swapin error swap entry,
> then we save one more swap entry slot for swap devices.  A new pte marker
> bit is defined.

Per my understanding, "swap entry" describes one swap page (4KB on x86)
in one swap device.  So, the original swapin error implementation uses
one swap file (or swap device) instead of one swap entry.  So your patch
saves one swap file (or swap device).

Best Regards,
Huang, Ying

> One thing worth mentioning: we need the pte marker to be always built to
> make sure it works like before, so I made an attempt in patch 1 to drop
> CONFIG_PTE_MARKER and always compile pte marker in.  Since pte markers are
> enabled in many distributions by default already, meanwhile the codeset is
> really small I assume it's fine.  But still I'm tagging with RFC for this
> initial version.
>
> Smoke tested on anonymous mem on a fake swap failure.  Please have a look,
> thanks.
>
> Peter Xu (2):
>   mm: Always compile in pte markers
>   mm: Use pte markers for swap errors
>
>  include/linux/swap.h    | 16 ++++----------
>  include/linux/swapops.h | 49 +++++++++--------------------------------
>  mm/Kconfig              |  7 ------
>  mm/memory.c             | 13 ++++++-----
>  mm/shmem.c              |  2 +-
>  mm/swapfile.c           |  2 +-
>  6 files changed, 23 insertions(+), 66 deletions(-)