--Lee Revell <[email protected]> wrote (on Saturday, June 25, 2005 14:08:25 -0400):
> On Fri, 2005-06-24 at 23:42 -0700, Martin J. Bligh wrote:
>> > (btw., if the TSC is that unreliable on numaq boxes, shouldnt we disable
>> > it for userspace apps too? Or are those hangs purely kernel bugs? In
>> > which case it might make sense to debug those a bit more - large-scale
>> > TSC unsyncedness is something that could slip in on other hardware too.)
>>
>> Well it reads reliably. it just reliably reads utter random crap (well,
>> across CPUs). Not many things read tsc from userspace, and it won't hang
>> I guess .... depends what their expecations are. I do like gettimeofday
>> not to go backwards though - that tends to bugger things up ;-)
>
> The userspace apps that read the TSC know what they are doing, and have
> chosen to use the TSC because they need a cheap, fast timer rather than
> a correct one. Please don't break it.
I have no intent, nor method, of doing so. rdtsc is a direct instruction,
without intervention, as I understand it.
M.
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