From: Avi Kivity <avi@argo.co.il>
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 TRY#3] optimize and simplify get_cycles_sync()
Date: Fri, 09 Mar 2007 20:10:03 +0200 [thread overview]
Message-ID: <45F1A2FB.7040206@argo.co.il> (raw)
In-Reply-To: <20070309151511.GE13481@amd.com>
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?
--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.
next prev parent reply other threads:[~2007-03-09 18:10 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 [this message]
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
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