From: "Joerg Roedel" <joerg.roedel@amd.com>
To: "Avi Kivity" <avi@argo.co.il>
Cc: discuss@x86-64.org, "Andi Kleen" <ak@suse.de>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 4/4 TRY#3] optimize and simplify get_cycles_sync()
Date: Mon, 12 Mar 2007 17:24:05 +0100 [thread overview]
Message-ID: <20070312162405.GA21463@amd.com> (raw)
In-Reply-To: <45F57AEB.5030405@argo.co.il>
On Mon, Mar 12, 2007 at 06:08:11PM +0200, Avi Kivity wrote:
> Joerg Roedel wrote:
> >On Fri, Mar 09, 2007 at 08:10:03PM +0200, Avi Kivity wrote:
> >
> >>Joerg Roedel 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.
> >>>
> >>> +#define RDTSCP ".byte 0x0f, 0x01, 0xf9"
> >>>+ alternative_io_two("cpuid\nrdtsc",
> >>>+ "rdtsc", X86_FEATURE_SYNC_RDTSC,
> >>>+ ".byte 0x0f, 0x01, 0xf9", X86_FEATURE_RDTSCP,
> >>>
> >>why not use the RDTSCP macro here?
> >>
> >
> >Does this macro exist? I couldn't found it in the current git tree. And
> >the rdtscp macros in msr.h use the plain opcode too.
> >
>
> -ENOCOFFEE? You defined the macro 3 lines above the .byte directive...
Yes, lack of coffee, and even worse -EBLINDHACKER :-(
--
Joerg Roedel
Operating System Research Center
AMD Saxony LLC & Co. KG
prev parent reply other threads:[~2007-03-12 16:26 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-03-09 15:08 [PATCH 0/4 TRY#3] improve alternative instruction code and optimize get_cycles_sync Joerg Roedel
2007-03-09 15:11 ` [PATCH 1/4 TRY#3] i386: extend alternative instructions framework Joerg Roedel
2007-03-09 15:12 ` [PATCH 2/4 TRY#3] x86_64: changes to x86_64 architecture for alternative instruction improvements Joerg Roedel
2007-03-09 15:13 ` [PATCH 3/4 TRY#3] i386: add the X86_FEATURE_SYNC_RDTSC flag Joerg Roedel
2007-03-09 15:15 ` [PATCH 4/4 TRY#3] optimize and simplify get_cycles_sync() Joerg Roedel
2007-03-09 18:10 ` Avi Kivity
2007-03-12 13:02 ` Joerg Roedel
2007-03-12 13:09 ` [discuss] " Andi Kleen
2007-03-12 13:21 ` Joerg Roedel
2007-03-12 13:29 ` Michael Matz
2007-03-12 13:45 ` Joerg Roedel
2007-03-12 16:08 ` Avi Kivity
2007-03-12 16:24 ` Joerg Roedel [this message]
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