linux-kernel - [PATCH 0/2] Implement arm64 specific huge_ptep

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Message-Id: <cover.1652180088.git.baolin.wang@linux.alibaba.com>
Date:   Tue, 10 May 2022 19:12:51 +0800
From:   Baolin Wang <baolin.wang@...ux.alibaba.com>
To:     catalin.marinas@....com, will@...nel.org, mike.kravetz@...cle.com,
        akpm@...ux-foundation.org
Cc:     songmuchun@...edance.com, willy@...radead.org,
        anshuman.khandual@....com, christophe.leroy@...roup.eu,
        baolin.wang@...ux.alibaba.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: [PATCH 0/2] Implement arm64 specific huge_ptep_get()

Hi,

As Mike pointed out [1], the huge_ptep_get() will only return one specific
pte value for the CONT-PTE or CONT-PMD size hugetlb on ARM64 system, which
will not take into account the subpages' dirty or young bits of a CONT-PTE/PMD
size hugetlb page. That will make us miss dirty or young flags of a CONT-PTE/PMD
size hugetlb page for those functions that want to check the dirty or
young flags of a hugetlb page. For example, the gather_hugetlb_stats() will
get inaccurate dirty hugetlb page statistics, and the DAMON for hugetlb monitoring
will also get inaccurate access statistics.

To fix this issue, this patch set introduces an ARM64 specific huge_ptep_get()
implementation, which will take into account any subpages' dirty or young bits.

[1] https://lore.kernel.org/linux-mm/85bd80b4-b4fd-0d3f-a2e5-149559f2f387@oracle.com/

Changes from RFC:
 - Implement arm64 specific huge_ptep_get() instead of introducing a new interface.
 - Add a new patch to convert huge_ptep_get() in hugetlbpage.c

Baolin Wang (2):
  arm64/hugetlb: Use ptep_get() to get the pte value of a huge page
  arm64/hugetlb: Implement arm64 specific huge_ptep_get()

 arch/arm64/include/asm/hugetlb.h |  2 ++
 arch/arm64/mm/hugetlbpage.c      | 32 ++++++++++++++++++++++++++++----
 2 files changed, 30 insertions(+), 4 deletions(-)

-- 
1.8.3.1