linux-kernel - Re: [PATCH mm-unstable v2 00/10] mm/kvm: locklessly clear the accessed bit

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Date:   Fri, 9 Jun 2023 11:07:55 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Yu Zhao <yuzhao@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Alistair Popple <apopple@...dia.com>,
        Anup Patel <anup@...infault.org>,
        Ben Gardon <bgardon@...gle.com>,
        Borislav Petkov <bp@...en8.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Chao Peng <chao.p.peng@...ux.intel.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Fabiano Rosas <farosas@...ux.ibm.com>,
        Gaosheng Cui <cuigaosheng1@...wei.com>,
        Gavin Shan <gshan@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        James Morse <james.morse@....com>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Jonathan Corbet <corbet@....net>,
        Marc Zyngier <maz@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Michael Larabel <michael@...haellarabel.com>,
        Mike Rapoport <rppt@...nel.org>,
        Nicholas Piggin <npiggin@...il.com>,
        Oliver Upton <oliver.upton@...ux.dev>,
        Paul Mackerras <paulus@...abs.org>,
        Peter Xu <peterx@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Thomas Huth <thuth@...hat.com>, Will Deacon <will@...nel.org>,
        Zenghui Yu <yuzenghui@...wei.com>, kvmarm@...ts.linux.dev,
        kvm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linuxppc-dev@...ts.ozlabs.org,
        linux-trace-kernel@...r.kernel.org, x86@...nel.org,
        linux-mm@...gle.com
Subject: Re: [PATCH mm-unstable v2 00/10] mm/kvm: locklessly clear the
 accessed bit

On 5/27/23 01:44, Yu Zhao wrote:
> TLDR
> ====
> This patchset adds a fast path to clear the accessed bit without
> taking kvm->mmu_lock. It can significantly improve the performance of
> guests when the host is under heavy memory pressure.
> 
> ChromeOS has been using a similar approach [1] since mid 2021 and it
> was proven successful on tens of millions devices.
> 
> This v2 addressed previous requests [2] on refactoring code, removing
> inaccurate/redundant texts, etc.
> 
> [1]https://crrev.com/c/2987928
> [2]https://lore.kernel.org/r/20230217041230.2417228-1-yuzhao@google.com/

 From the KVM point of view the patches look good (though I wouldn't 
mind if Nicholas took a look at the ppc part).  Jason's comment on the 
MMU notifier side are promising as well.  Can you send v3 with Oliver's 
comments addressed?

Thanks,

Paolo