Messages in this thread | | | Date | Tue, 29 Nov 2005 17:48:58 +0100 | From | Andi Kleen <> | Subject | Re: [RT] read_tsc: ACK! TSC went backward! Unsynced TSCs? |
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On Tue, Nov 29, 2005 at 08:52:19AM -0800, thockin@hockin.org wrote: > On Tue, Nov 29, 2005 at 07:06:24AM -0700, Andi Kleen wrote: > > But I'm surprised you're saying 2.6.11 broke. At least 2.6.11 64bit should > > have always used HPET in this case. I only broke it around 2.6.13 > > where I added an overeager optimization for single socket DC on my side based > > on a misunderstanding. Earlier and later kernels should have been ok. > > we didn't have HPET enabled in BIOS until recently. Turning that on made > all the TSC gettimeofday() crap disappear. Now to find and kill any > straggling users of rdtsc
The newer kernels work around this too by using pmtimer when needed. Of course it's slow.
Regarding straggling users of rdtsc - one way would be to optionally trap them and log them in the kernel. That would work in ring 3 at least.
-Andi
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