Messages in this thread | | | Date | Wed, 14 Nov 2007 15:26:29 +0100 | From | Andi Kleen <> | Subject | Re: [perfmon] Re: [perfmon2] perfmon2 merge news |
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On Wed, Nov 14, 2007 at 06:13:42AM -0800, Stephane Eranian wrote: > > At least for x86 and I suspect some 1other architectures we don't > > initially need a syscall at all for this. There is an instruction > > RDPMC who can read a performance counter just fine. It is also much > > faster and generally preferable for the case where a process measures > > events about itself. In fact it is essential for one of the use cases > > I would like to see perfmon used (replacement of RDTSC for cycle > > counting) > > > > This only works when counting (not sampling) and only for self-monitoring.
It works for global monitoring too.
> > > Later a syscall might be needed with event multiplexing, but that seems > > more like a far away non essential feature. > > > On a machine with only two generic counters such as MIPS or Intel Core 2 Duo, > multiplexing offers some advantages. If NMI watchdog is enabled, then you drop > to one generic counter on on Core 2.
NMI watchdog is off by default now.
Yes longer term we might need multiplexing, but definitely not as first step.
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