Tony, On Wed, Jan 03, 2007 at 10:19:34AM -0800, Luck, Tony wrote: > > These experiments should be run twice: one set with an event that is > > only triggered in the user-space (e.g. FP op counting) and a second > > set an event that occurs both in kernel and user space. > > Some architectures do some floating point operations in the > kernel (e.g. ia64 ... gcc generates code that uses the FPU for > integer multiply). So you may not be able to use a strictly > "kernel count must be zero" for FP operation events. > Yes.
> Perhaps this can be inverted ... find an event that is only triggered > by a privileged instruction ... so you can see some "kernel only" > counting happening. Still have the problem of determining whether > the value you see is sane. You could compare results across different > time intervals (while running the same load) and check that the counts > scale correctly. > I am not sure we can find an event that can only be triggered by privileged code and which would exist across X86, IA-64 to a bare minimum, especially if you consider the various flavors of X86. If you limit yourself to Ia-64 and Core 2 Duo, then you may be able to find something interrupt or VM related. -- -Stephane _______________________________________________ perfmon mailing list [email protected] http://www.hpl.hp.com/hosted/linux/mail-archives/perfmon/
