linux-kernel - Re: [PATCH v2] RFC: clear 1G pages with streaming stores on x86

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Date:   Mon, 30 Jul 2018 17:28:37 -0700
From:   Cannon Matthews <cannonmatthews@...gle.com>
To:     bp@...en8.de
Cc:     mhocko@...nel.org, mike.kravetz@...cle.com,
        akpm@...ux-foundation.org, willy@...radead.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Andres Lagar-Cavilla <andreslc@...gle.com>,
        Salman Qazi <sqazi@...gle.com>, Paul Turner <pjt@...gle.com>,
        David Matlack <dmatlack@...gle.com>,
        Peter Feiner <pfeiner@...gle.com>,
        Alain Trinh <nullptr@...gle.com>
Subject: Re: [PATCH v2] RFC: clear 1G pages with streaming stores on x86

Thanks for all the feedback from everyone.

I am going to try to fix this up, and do some more robust benchmarking,
including the 2MB case, and try to have an updated/non-RFC patch(es) in
a few days.

Thanks!
Cannon
On Mon, Jul 30, 2018 at 9:29 AM Borislav Petkov <bp@...en8.de> wrote:
>
> On Tue, Jul 24, 2018 at 07:37:28PM -0700, Cannon Matthews wrote:
> > diff --git a/arch/x86/lib/clear_page_64.S b/arch/x86/lib/clear_page_64.S
> > index 88acd349911b..81a39804ac72 100644
> > --- a/arch/x86/lib/clear_page_64.S
> > +++ b/arch/x86/lib/clear_page_64.S
> > @@ -49,3 +49,23 @@ ENTRY(clear_page_erms)
> >       ret
> >  ENDPROC(clear_page_erms)
> >  EXPORT_SYMBOL_GPL(clear_page_erms)
> > +
> > +/*
> > + * Zero memory using non temporal stores, bypassing the cache.
> > + * Requires an `sfence` (wmb()) afterwards.
> > + * %rdi - destination.
> > + * %rsi - page size. Must be 64 bit aligned.
> > +*/
> > +ENTRY(__clear_page_nt)
> > +     leaq    (%rdi,%rsi), %rdx
> > +     xorl    %eax, %eax
> > +     .p2align 4,,10
> > +     .p2align 3
> > +.L2:
> > +     movnti  %rax, (%rdi)
> > +     addq    $8, %rdi
> > +     cmpq    %rdx, %rdi
> > +     jne     .L2
> > +     ret
> > +ENDPROC(__clear_page_nt)
> > +EXPORT_SYMBOL(__clear_page_nt)
>
> EXPORT_SYMBOL_GPL like the other functions in that file.
>
> --
> Regards/Gruss,
>     Boris.
>
> ECO tip #101: Trim your mails when you reply.
> --