linux-kernel - Re: [PATCH 5/8] x86/clear_page: add clear_page

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Message-ID: <593f3b75-678c-1cd4-a7f0-55257dc84caf@oracle.com>
Date:   Thu, 15 Oct 2020 14:20:36 -0700
From:   Ankur Arora <ankur.a.arora@...cle.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Andy Lutomirski <luto@...capital.net>,
        Andy Lutomirski <luto@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        Michal Hocko <mhocko@...nel.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, X86 ML <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, Arnd Bergmann <arnd@...db.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Ira Weiny <ira.weiny@...el.com>,
        linux-arch <linux-arch@...r.kernel.org>
Subject: Re: [PATCH 5/8] x86/clear_page: add clear_page_uncached()

On 2020-10-15 3:35 a.m., Borislav Petkov wrote:
> On Wed, Oct 14, 2020 at 08:37:44PM -0700, Ankur Arora wrote:
>> I don't disagree but I think the selection of cached/uncached route should
>> be made where we have enough context available to be able to choose to do
>> this.
>>
>> This could be for example, done in mm_populate() or gup where if say the
>> extent is larger than LLC-size, it takes the uncached path.
> 
> Are there examples where we don't know the size?

The case I was thinking of was that clear_huge_page() or faultin_page() would
know the size to a page unit, while the higher level function would know the
whole extent and could optimize differently based on that.

Thanks
Ankur

>