Re: [discuss] Re: [PATCH] Allow all Opteron processors to changepstateat same time

From: Bhavana Nagendra
Date: Thu Jul 13 2006 - 10:59:19 EST


Here are some results without changing frequencies on a system whose BIOS does not support Power Now! on MP systems:

Basically the system booted up with "nohpet, nopmtimer"i.e. using TSC as the GTOD time source and system stayed idle for 13 hours. There appears to be drift of 20 secs in the CPU 2 readings. This TSC drift could worsen when
the system is active and doing GTOD operations and/or when system is up a lot longer.

CPU 2: Syncing TSC to CPU 0.
CPU 2: synchronized TSC with CPU 0 (last diff -108 cycles, maxerr 826 cycles)
CPU 3: Syncing TSC to CPU 0.
CPU 3: synchronized TSC with CPU 0 (last diff -119 cycles, maxerr 845 cycles)

*** CPUs go offline ***

*** back online ***

CPU 2: Syncing TSC to CPU 0.
CPU 2: synchronized TSC with CPU 0 (last diff -117 cycles, maxerr 846 cycles)
CPU 3: Syncing TSC to CPU 0.
CPU 3: synchronized TSC with CPU 0 (last diff -117 cycles, maxerr 845 cycles)

shin, jacob wrote:

On Thursday, July 13, 2006 9:32 AM Deguara, Joachim wrote:



parallel sounds fun, but I don't get it. Two machine or trying to go
online and offline at the same time? Firestorming two busy parallel
while loops, one turning the core offline and the other online, did
not bring an oops so I guess this kernel is in the clear in that
regard.

I can't get it to crash again and I am afraid that it crashed under an
old devel kernel. After another ~20 hour test with heavy freq changes
with the tscsync patch



There were several different issues w/ powernow + cpu hotplug in the
past. Good to hear that the latest kernel doesn't oops.. I believe cpu hotplug is needed for suspend to work..





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