linux-kernel - Re: mm: delay rmap removal until after TLB flush

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Message-ID: <CAHk-=wh6MxaCA4pXpt1F5Bn2__6MxCq0Dr-rES4i=MOL9ibjpg@mail.gmail.com>
Date:   Mon, 7 Nov 2022 15:47:38 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Johannes Weiner <hannes@...xchg.org>
Cc:     Hugh Dickins <hughd@...gle.com>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Will Deacon <will@...nel.org>,
        Aneesh Kumar <aneesh.kumar@...ux.ibm.com>,
        Nick Piggin <npiggin@...il.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Jann Horn <jannh@...gle.com>,
        John Hubbard <jhubbard@...dia.com>, X86 ML <x86@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        kernel list <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Joerg Roedel <jroedel@...e.de>,
        Uros Bizjak <ubizjak@...il.com>,
        Alistair Popple <apopple@...dia.com>,
        linux-arch <linux-arch@...r.kernel.org>
Subject: Re: mm: delay rmap removal until after TLB flush

On Mon, Nov 7, 2022 at 12:29 PM Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> That said, if always doing the rmap removal under the page table lock
> means that that memcg lock can just be deleted in that whole path, I
> will certainly bow to _that_ simplification instead, and just handle
> the dirty pages after the TLB flush but before the page table drop.

Ok, so I think I have a fairly clean way to do this.

Let me try to make that series look reasonable, although it might be
until tomorrow. I'll need to massage my mess into not just prettier
code, but a sane history.

               Linus