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References: <20230810103332.3062143-1-ryan.roberts@arm.com> <20230810103332.3062143-4-ryan.roberts@arm.com>
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From:   Yu Zhao <yuzhao@google.com>
Date:   Thu, 10 Aug 2023 11:34:57 -0600
Message-ID: <CAOUHufZatMprwzaT+=Lb6jSw60DN_Br=Og+N6krK3OQZiGyAYA@mail.gmail.com>
Subject: Re: [PATCH v1 3/4] mm/mmu_gather: Remove encoded_page infrastructure
To:     Ryan Roberts <ryan.roberts@arm.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Hugh Dickins <hughd@google.com>,
        Johannes Weiner <hannes@cmpxchg.org>
Cc:     Will Deacon <will@kernel.org>,
        "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Nick Piggin <npiggin@gmail.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Christian Borntraeger <borntraeger@linux.ibm.com>,
        Sven Schnelle <svens@linux.ibm.com>,
        Arnd Bergmann <arnd@arndb.de>,
        "Matthew Wilcox (Oracle)" <willy@infradead.org>,
        David Hildenbrand <david@redhat.com>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Yin Fengwei <fengwei.yin@intel.com>,
        Yang Shi <shy828301@gmail.com>,
        "Huang, Ying" <ying.huang@intel.com>, Zi Yan <ziy@nvidia.com>,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org
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On Thu, Aug 10, 2023 at 4:33=E2=80=AFAM Ryan Roberts <ryan.roberts@arm.com>=
 wrote:
>
> commit 70fb4fdff582 ("mm: introduce 'encoded' page pointers with
> embedded extra bits") and commit 7cc8f9c7146a ("mm: mmu_gather: prepare
> to gather encoded page pointers with flags") converted mmu_gather for
> dealing with encoded_page, where the bottom 2 bits could encode extra
> flags. Only 1 bit was ever used; to flag whether the page should
> participate in a delayed rmap removal.
>
> Now that the mmu_gather batched rmap removal mechanism has been
> generalized, all pages participate and therefore the flag is unused. So
> let's remove encoded_page to simplify the code. It also gets in the way
> of further optimization which will be done in a follow up patch.

Adding the original author and reviewers... They might want (need) to
take a look at this series.