From: Matthew Wilcox <willy@infradead.org>
To: Andi Kleen <ak@linux.intel.com>
Cc: Michal Hocko <mhocko@kernel.org>,
"Kirill A. Shutemov" <kirill@shutemov.name>,
Cannon Matthews <cannonmatthews@google.com>,
Mike Kravetz <mike.kravetz@oracle.com>,
Andrew Morton <akpm@linux-foundation.org>,
David Rientjes <rientjes@google.com>,
Greg Thelen <gthelen@google.com>, Salman Qazi <sqazi@google.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org, x86@kernel.org
Subject: Re: [PATCH] mm: clear 1G pages with streaming stores on x86
Date: Mon, 9 Mar 2020 11:37:04 -0700 [thread overview]
Message-ID: <20200309183704.GA1573@bombadil.infradead.org> (raw)
In-Reply-To: <20200309153831.GK1454533@tassilo.jf.intel.com>
On Mon, Mar 09, 2020 at 08:38:31AM -0700, Andi Kleen wrote:
> > Gigantic huge pages are a bit different. They are much less dynamic from
> > the usage POV in my experience. Micro-optimizations for the first access
> > tends to not matter at all as it is usually pre-allocation scenario. On
> > the other hand, speeding up the initialization sounds like a good thing
> > in general. It will be a single time benefit but if the additional code
> > is not hard to maintain then I would be inclined to take it even with
> > "artificial" numbers state above. There really shouldn't be other downsides
> > except for the code maintenance, right?
>
> 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.
>
> String instructions are constantly improving in performance (Broadwell is
> very old at this point) Most likely over time (and maybe even today
> on newer CPUs) you would need much more sophisticated unrolled MOVNTI variants
> (or maybe even AVX-*) to be competitive.
Presumably you have access to current and maybe even some unreleased
CPUs ... I mean, he's posted the patches, so you can test this hypothesis.
next prev parent reply other threads:[~2020-03-09 18:37 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-07 1:03 [PATCH] mm: clear 1G pages with streaming stores on x86 Cannon Matthews
2020-03-07 22:06 ` Andrew Morton
2020-03-09 0:08 ` Kirill A. Shutemov
2020-03-09 9:06 ` Michal Hocko
2020-03-09 9:35 ` Kirill A. Shutemov
2020-03-09 11:36 ` Kirill A. Shutemov
2020-03-09 12:26 ` Michal Hocko
2020-03-09 18:01 ` Mike Kravetz
2020-03-09 15:38 ` Andi Kleen
2020-03-09 18:37 ` Matthew Wilcox [this message]
2020-03-11 0:21 ` Cannon Matthews
2020-03-11 0:54 ` Kirill A. Shutemov
2020-03-11 3:35 ` Arvind Sankar
2020-03-11 8:16 ` Kirill A. Shutemov
2020-03-11 18:32 ` Arvind Sankar
2020-03-11 20:32 ` Arvind Sankar
2020-03-12 0:52 ` Kirill A. Shutemov
2020-03-31 0:40 ` Elliott, Robert (Servers)
2020-03-16 10:18 ` Michal Hocko
2020-03-16 12:19 ` Kirill A. Shutemov
2020-03-26 19:46 ` Matthew Wilcox
2020-03-11 15:07 ` David Laight
2020-03-09 15:33 ` Andi Kleen
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