Re: [PATCH RFC] [X86] performance improvement for memcpy_64.S by fast string.

From: Andi Kleen <andi@firstfloor.org>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: "Ma, Ling" <ling.ma@intel.com>, Ingo Molnar <mingo@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH RFC] [X86] performance improvement for memcpy_64.S by fast string.
Date: Mon, 09 Nov 2009 10:26:14 +0100	[thread overview]
Message-ID: <87ws2059s9.fsf@basil.nowhere.org> (raw)
In-Reply-To: <4AF7C66C.6000009@zytor.com> (H. Peter Anvin's message of "Sun, 08 Nov 2009 23:36:12 -0800")

"H. Peter Anvin" <hpa@zytor.com> writes:
>
> My personal opinion is that if we can show no significant slowdown on
> P4, K8, P-M/Core 1, Core 2, and Nehalem then we can simply use this code

The issue is Core 2.

P4 uses a different path, and Core 1 doesn't use the 64bit code.

> unconditionally.  If one of them is radically worse than baseline, then
> we have to do something conditional, which is a lot more complicated.

I have an older patchkit which did this, and some more optimizations
to this code.

There was still one open issue, that is why I didn't post it. If there's
interest I can post it.

-Andi
-- 
ak@linux.intel.com -- Speaking for myself only.