Messages in this thread | | | Date | Fri, 30 Jun 2006 13:40:32 -0700 | From | Stephane Eranian <> | Subject | Re: [PATCH 10/17] 2.6.17.1 perfmon2 patch for review: PMU context switch |
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Chuck,
On Fri, Jun 30, 2006 at 02:33:49PM -0400, Chuck Ebbert wrote: > In-Reply-To: <200606301541.22928.ak@suse.de> > > On Fri, 30 Jun 2006 15:41:22 +0200, Andi Kleen wrote: > > > > So why do we need care about context switch in cpu-wide mode? > > > It is because we support a mode where the idle thread is excluded > > > from cpu-wide monitoring. This is very useful to distinguish > > > 'useful kernel work' from 'idle'. > > > > I don't quite see the point because on x86 the PMU doesn't run > > during C states anyways. So you get idle excluded automatically. > > Looks like it does run: > > $ pfmon -ecpu_clk_unhalted,interrupts_masked_cycles -k --system-wide -t 10 > <session to end in 10 seconds> > CPU0 60351837 CPU_CLK_UNHALTED > CPU0 346548229 INTERRUPTS_MASKED_CYCLES > > The CPU spent ~60 million clocks unhalted and ~350 million with interrupts > disabled. (This is an idle 1.6GHz Turion64 machine.) >
As Andi is suggesting, I think this may depends on how the BIOS implements the low-power state. I have tried the same command on my dual Opteron 250 2.4GHz and I get: $ pfmon --us-c -ecpu_clk_unhalted,interrupts_masked_cycles -k --system-wide -t 10 <session to end in 10 seconds> CPU0 9,520,303 CPU_CLK_UNHALTED CPU0 3,726,315 INTERRUPTS_MASKED_CYCLES CPU1 21,268,151 CPU_CLK_UNHALTED CPU1 14,515,389 INTERRUPTS_MASKED_CYCLES
That's without idle=poll.
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