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Date:   Tue, 13 Apr 2021 13:01:37 +0200
From:   Borislav Petkov <bp@alien8.de>
To:     Kemeng Shi <shikemeng@huawei.com>
Cc:     tglx@linutronix.de, mingo@redhat.com, x86@kernel.org,
        hpa@zytor.com, linux-kernel@vger.kernel.org,
        linux-nvdimm@lists.01.org
Subject: Re: [PATCH] x86: Accelerate copy_page with non-temporal in X86
Message-ID: <20210413110137.GD16519@zn.tnic>
References: <3f28adee-8214-fa8e-b368-eaf8b193469e@huawei.com>
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+ linux-nvdimm

Original mail at https://lkml.kernel.org/r/3f28adee-8214-fa8e-b368-eaf8b193469e@huawei.com

On Tue, Apr 13, 2021 at 02:25:58PM +0800, Kemeng Shi wrote:
> I'm using AEP with dax_kmem drvier, and AEP is export as a NUMA node in

What is AEP?

> my system. I will move cold pages from DRAM node to AEP node with
> move_pages system call. With old "rep movsq', it costs 2030ms to move
> 1 GB pages. With "movnti", it only cost about 890ms to move 1GB pages.

So there's __copy_user_nocache() which does NT stores.

> -	ALTERNATIVE "jmp copy_page_regs", "", X86_FEATURE_REP_GOOD
> +	ALTERNATIVE_2 "jmp copy_page_regs", "", X86_FEATURE_REP_GOOD, \
> +                      "jmp copy_page_nt", X86_FEATURE_XMM2

This makes every machine which has sse2 do NT stores now. Which means
*every* machine practically.

The folks on linux-nvdimm@ should be able to give you a better idea what
to do.

HTH.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette