linux-kernel - Re: [PATCH v14 08/14] mm: multi-gen LRU: support page table walks

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Message-ID: <Y1GZjPO+szk7X0wP@hirez.programming.kicks-ass.net>
Date:   Thu, 20 Oct 2022 20:55:08 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Yu Zhao <yuzhao@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Aneesh Kumar <aneesh.kumar@...ux.ibm.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Hillf Danton <hdanton@...a.com>, Jens Axboe <axboe@...nel.dk>,
        Johannes Weiner <hannes@...xchg.org>,
        Jonathan Corbet <corbet@....net>,
        Matthew Wilcox <willy@...radead.org>,
        Mel Gorman <mgorman@...e.de>,
        Michael Larabel <Michael@...haellarabel.com>,
        Michal Hocko <mhocko@...nel.org>,
        Mike Rapoport <rppt@...nel.org>, Tejun Heo <tj@...nel.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Will Deacon <will@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org,
        page-reclaim@...gle.com, Brian Geffon <bgeffon@...gle.com>,
        Jan Alexander Steffens <heftig@...hlinux.org>,
        Oleksandr Natalenko <oleksandr@...alenko.name>,
        Steven Barrett <steven@...uorix.net>,
        Suleiman Souhlal <suleiman@...gle.com>,
        Daniel Byrne <djbyrne@....edu>,
        Donald Carr <d@...os-reins.com>,
        Holger Hoffstätte 
        <holger@...lied-asynchrony.com>,
        Konstantin Kharlamov <Hi-Angel@...dex.ru>,
        Shuang Zhai <szhai2@...rochester.edu>,
        Sofia Trinh <sofia.trinh@....works>,
        Vaibhav Jain <vaibhav@...ux.ibm.com>
Subject: Re: [PATCH v14 08/14] mm: multi-gen LRU: support page table walks

On Thu, Oct 20, 2022 at 10:35:28AM -0700, Linus Torvalds wrote:
> On Thu, Oct 20, 2022 at 7:14 AM Peter Zijlstra <peterz@...radead.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()"?

Yep -- it's *that* old :-/ You're not in fact the first to point that
out.

I'll make time tomorrow to fix it up and respin and send out. This is as
good a time as any to get rid of carrying these patches myself.