Messages in this thread | | | Date | Thu, 27 Nov 2008 19:41:49 +0100 | From | Andi Kleen <> | Subject | Re: [patch 02/24] perfmon: base code |
| |
> Well, where is it checked ? Where is checked whether Oprofile runs or not ?
That is done using the perfctr reservation. I saw that somewhere in the patchkit. The NMI watchdog uses that too.
> > The Oprofile reservation you see is built on top of the cpumask reservation. > > It tries to allocate in one call and atomically ALL the CPUs as this is the way > > Oprofile operates. Thus it fails if one perfmon system-wide session or one > > perfmon per-thread exists. > > This only prevents oprofile from starting, but it does neither prevent > thread sessions nor does it prevent a perfmon per cpu session on a cpu > which was onlined after oprofile started, simply because it's bit is > missing in the CPU mask.
The perfctr reservation is global over all CPUs.
-Andi
-- ak@linux.intel.com
| |