linux-kernel - Re: [PATCH v1 3/4] mm/mmu_gather: Remove encoded

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Message-ID: <CAOUHufZatMprwzaT+=Lb6jSw60DN_Br=Og+N6krK3OQZiGyAYA@mail.gmail.com>
Date:   Thu, 10 Aug 2023 11:34:57 -0600
From:   Yu Zhao <yuzhao@...gle.com>
To:     Ryan Roberts <ryan.roberts@....com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Hugh Dickins <hughd@...gle.com>,
        Johannes Weiner <hannes@...xchg.org>
Cc:     Will Deacon <will@...nel.org>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Nick Piggin <npiggin@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Arnd Bergmann <arnd@...db.de>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        David Hildenbrand <david@...hat.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Yin Fengwei <fengwei.yin@...el.com>,
        Yang Shi <shy828301@...il.com>,
        "Huang, Ying" <ying.huang@...el.com>, Zi Yan <ziy@...dia.com>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 3/4] mm/mmu_gather: Remove encoded_page infrastructure

On Thu, Aug 10, 2023 at 4:33 AM Ryan Roberts <ryan.roberts@....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.