linux-kernel - Re: [PATCH v5 0/6] Add hardware prefetch control driver for A64FX and x86

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Date:   Fri, 10 Jun 2022 15:07:26 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Kohei Tarumizu <tarumizu.kohei@...itsu.com>
Cc:     catalin.marinas@....com, will@...nel.org, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
        x86@...nel.org, hpa@...or.com, rafael@...nel.org, lenb@...nel.org,
        mchehab+huawei@...nel.org, eugenis@...gle.com, tony.luck@...el.com,
        pcc@...gle.com, peterz@...radead.org, marcos@...a.pet,
        marcan@...can.st, linus.walleij@...aro.org,
        nicolas.ferre@...rochip.com, conor.dooley@...rochip.com,
        arnd@...db.de, ast@...nel.org, peter.chen@...nel.org,
        kuba@...nel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-acpi@...r.kernel.org
Subject: Re: [PATCH v5 0/6] Add hardware prefetch control driver for A64FX
 and x86

On Tue, Jun 07, 2022 at 09:05:24PM +0900, Kohei Tarumizu wrote:
> This patch series add sysfs interface to control CPU's hardware
> prefetch behavior for performance tuning from userspace for the
> processor A64FX and x86 (on supported CPU).

Why does userspace want to even do this?

How will they do this?

What programs will do this?

And why isn't just automatic and why does this hardware require manual
intervention to work properly?

thanks,

greg k-h