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From: Andrew Morton <akpm@linux-foundation.org>
To: "Joerg Roedel" <joerg.roedel@amd.com>
Cc: discuss@x86-64.org, "Andi Kleen" <ak@suse.de>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 4/4] optimize and simplify get_cycles_sync()
Date: Tue, 6 Mar 2007 16:25:41 -0800	[thread overview]
Message-ID: <20070306162541.2b8a148d.akpm@linux-foundation.org> (raw)
In-Reply-To: <20070228142554.GE19452@amd.com>

On Wed, 28 Feb 2007 15:25:54 +0100
"Joerg Roedel" <joerg.roedel@amd.com> wrote:

> From: Joerg Roedel <joerg.roedel@amd.com>
> 
> This patch simplifies the get_cycles_sync() function by removing the
> #ifdefs from it. Further it introduces an optimization for AMD
> processors. There the RDTSCP instruction is used instead of CPUID;RDTSC
> which is helpfull if the kernel runs as a KVM guest. Running as a guest
> makes CPUID very expensive because it causes an intercept of the guest.

Problem:

http://test.kernel.org/functional/index.html

lots of builds fell over because their binutils versions don't understand
rdtscp.

I don't know how recently rdtscp support was added to binutils, but
this is likely to be a problem.  Perhaps we can change this patch to
embed the hex code for that opcode instead?

  reply	other threads:[~2007-03-07  0:25 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-02-28 14:05 [PATCH 0/4] improve alternative instruction code and optimize get_cycles_sync Joerg Roedel
2007-02-28 14:14 ` [PATCH 1/4] i386: extend alternative instructions framework Joerg Roedel
2007-02-28 14:18 ` [PATCH 2/4] x86_64: changes to x86_64 architecture for alternative instruction improvements Joerg Roedel
2007-02-28 14:21 ` [PATCH 3/4] i386: add the X86_FEATURE_SYNC_RDTSC flag Joerg Roedel
2007-02-28 14:25 ` [PATCH 4/4] optimize and simplify get_cycles_sync() Joerg Roedel
2007-03-07  0:25   ` Andrew Morton [this message]
2007-03-09  9:57     ` Joerg Roedel

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