In-Reply-To: <[email protected]>
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.)
Now let's see what happens when we exclude the idle thread:
$ pfmon -ecpu_clk_unhalted,interrupts_masked_cycles -k --system-wide -t 10 --excl-idle
<session to end in 10 seconds>
CPU0 449250 CPU_CLK_UNHALTED
CPU0 161577 INTERRUPTS_MASKED_CYCLES
Looks like excluding the idle thread means interrupts that happen while idle
don't get counted either. We took 5000 clock interrupts and I know they take
longer than that to process.
--
Chuck
"You can't read a newspaper if you can't read." --George W. Bush
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
