linux-kernel - RE: [PATCH] mm: clear 1G pages with streaming stores on x86

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Date:   Wed, 11 Mar 2020 15:07:07 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Andi Kleen' <ak@...ux.intel.com>, Michal Hocko <mhocko@...nel.org>
CC:     "Kirill A. Shutemov" <kirill@...temov.name>,
        Cannon Matthews <cannonmatthews@...gle.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        "Andrew Morton" <akpm@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>,
        David Rientjes <rientjes@...gle.com>,
        Greg Thelen <gthelen@...gle.com>,
        Salman Qazi <sqazi@...gle.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>
Subject: RE: [PATCH] mm: clear 1G pages with streaming stores on x86

From: Andi Kleen
> Sent: 09 March 2020 15:39
...
> There's a cautious tale of the old crappy RAID5 XOR assembler functions which
> were optimized a long time ago for the Pentium1, and stayed around,
> even though the compiler could actually do a better job.

Or the amd64 asm loop for doing the IP checksum.
I doubt it was even the fastest version when it was written.
A whole set of Intel cpus can run twice as fast as that version
with less loop unrolling (and associated code for 'odd' lengths).

	David

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