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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Thu, 20 Oct 2022 10:35:28 -0700
Message-ID: <CAHk-=whQchubuDpRGFabhmcZuzdt13OOF8wznXb+Dbi3GzBQhQ@mail.gmail.com>
Subject: Re: [PATCH v14 08/14] mm: multi-gen LRU: support page table walks
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     Yu Zhao <yuzhao@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andi Kleen <ak@linux.intel.com>,
        Aneesh Kumar <aneesh.kumar@linux.ibm.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Hillf Danton <hdanton@sina.com>, Jens Axboe <axboe@kernel.dk>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Jonathan Corbet <corbet@lwn.net>,
        Matthew Wilcox <willy@infradead.org>,
        Mel Gorman <mgorman@suse.de>,
        Michael Larabel <Michael@michaellarabel.com>,
        Michal Hocko <mhocko@kernel.org>,
        Mike Rapoport <rppt@kernel.org>, Tejun Heo <tj@kernel.org>,
        Vlastimil Babka <vbabka@suse.cz>,
        Will Deacon <will@kernel.org>,
        linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org,
        page-reclaim@google.com, Brian Geffon <bgeffon@google.com>,
        Jan Alexander Steffens <heftig@archlinux.org>,
        Oleksandr Natalenko <oleksandr@natalenko.name>,
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On Thu, Oct 20, 2022 at 7:14 AM Peter Zijlstra <peterz@infradead.org> wrote:
>
> So I've been sitting on these here patches (and never having time to
> repost them), which is how I noticed in the first place:
>
>   https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git/log/?h=x86/mm.pae

Well, that seems an improvement. I don't love how GUP_GET_PTE_LOW_HIGH
now affects the PMD too, but if it's ok for all the three users, I
guess it's ok. Maybe rename it now that it's not just the PTE?

That said, I reacted to that cmpxchg loop:

        } while (cmpxchg64(&pmdp->pmd, old.pmd, 0ULL) != old.pmd);

is this series just so old (but rebased) that it doesn't use "try_cmpxchg64()"?


               Linus