linux-kernel - Re: [RFC 0/6] x86: prefetch

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Message-Id: <D3DF6AC2-679F-4E64-B511-B1A03D1C6048@gmail.com>
Date:   Thu, 25 Feb 2021 01:32:56 -0800
From:   Nadav Amit <nadav.amit@...il.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Linux-MM <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>,
        Hugh Dickins <hughd@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Sean Christopherson <seanjc@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>, x86@...nel.org
Subject: Re: [RFC 0/6] x86: prefetch_page() vDSO call



> On Feb 25, 2021, at 12:52 AM, Nadav Amit <nadav.amit@...il.com> wrote:
> 
> 
> 
>> On Feb 25, 2021, at 12:40 AM, Peter Zijlstra <peterz@...radead.org> wrote:
>> 
>> On Wed, Feb 24, 2021 at 11:29:04PM -0800, Nadav Amit wrote:
>>> From: Nadav Amit <namit@...are.com>
>>> 
>>> Just as applications can use prefetch instructions to overlap
>>> computations and memory accesses, applications may want to overlap the
>>> page-faults and compute or overlap the I/O accesses that are required
>>> for page-faults of different pages.
[
[ snip ]

>> Interesting, but given we've been removing explicit prefetch from some
>> parts of the kernel how useful is this in actual use? I'm thinking there
>> should at least be a real user and performance numbers with this before
>> merging.
> 
> Can you give me a reference to the “removing explicit prefetch from some
> parts of the kernel”?

Oh. I get it - you mean we remove we remove the use of explicit memory
prefetch from the kernel code. Well, I don’t think it is really related,
but yes, performance numbers are needed.


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