Re: [PATCH] x86: Export tsc related information in sysfs

From: H. Peter Anvin
Date: Tue May 18 2010 - 12:45:11 EST

On 05/18/2010 04:58 AM, Peter Zijlstra wrote:
> On Tue, 2010-05-18 at 13:25 +0200, Andi Kleen wrote:
>> On Tue, May 18, 2010 at 11:58:18AM +0200, Peter Zijlstra wrote:
>>> On Sun, 2010-05-16 at 22:06 -0700, Arjan van de Ven wrote:
>>>> look we're not disabling ring 3 tsc. We could, but we don't.
>>> Maybe we should.
>> That would kill the vsyscall too. Remember it's running in ring 3.
>> That is in theory you could disable it on systems where the vsyscall
>> doesn't use it, but then you would likely break huge amounts of software,
>> unless you emulate it.
> Well, software shouldn't use it, so breaking it sounds like a fine
> idea ;-)
> Also, a slow emulation is an incentive to actually do the right thing.

The problem is that you throw the baby (vsyscall) out with the bathwater
(user rdtsc).


H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.

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