linux-kernel - Re: [PATCH] arm64: clear_page: use stnp non-temporal instruction for performance optimizing

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Message-ID: <YZP1qMj4dWCbDrN6@arm.com>
Date:   Tue, 16 Nov 2021 18:17:12 +0000
From:   Catalin Marinas <catalin.marinas@....com>
To:     Guanghui Feng <guanghuifeng@...ux.alibaba.com>
Cc:     will@...nel.org, maz@...nel.org, qperret@...gle.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        baolin.wang@...ux.alibaba.com, zhuo.song@...ux.alibaba.com,
        zhangliguang@...ux.alibaba.com
Subject: Re: [PATCH] arm64: clear_page: use stnp non-temporal instruction for
 performance optimizing

On Tue, Nov 16, 2021 at 11:08:14PM +0800, Guanghui Feng wrote:
> When clear page mem, there is no need to alloc cache for storing these
> mem value.

I theory, DC ZVA is supposed to trigger write streaming mode and all
writes go directly to memory avoiding cache allocation.

> And the copy_page.S have used stnp instruction for optimizing.
> So I rewrite the clear_page.S with stnp. At the same time, I have tested it
> with stnp instruction which will get about twice the performance improvement.

On which CPU implementation? Is the same improvement seen on a wider
range of CPUs?

-- 
Catalin