On Tue, Mar 19, 2019 at 03:47:48PM +0100, Peter Zijlstra wrote: > On Mon, Mar 18, 2019 at 02:41:25PM -0700, kan.li...@linux.intel.com wrote: > > From: Kan Liang <kan.li...@linux.intel.com> > > > > Adaptive PEBS is a new way to report PEBS sampling information. Instead > > of a fixed size record for all PEBS events it allows to configure the > > PEBS record to only include the information needed. Events can then opt > > in to use such an extended record, or stay with a basic record which > > only contains the IP. > > > > The major new feature is to support LBRs in PEBS record. > > This allows (much faster) large PEBS, while still supporting callstacks > > through callstack LBR. > > Does it also allow normal LBR usage? Or does it have to be callstacks?
It allows normal LBR too. But I would expect callstack to be the most common one. As long as you set a period you can get multi-record PEBS with -g, which has a lot lower lower overhead than using PMIs. Eventually I hope we can even make multi-record PEBS work in frequency mode by averaging the frequency over multiple records. > > hwc->config |= ARCH_PERFMON_EVENTSEL_INT; > > + hwc->config &= ~ICL_EVENTSEL_ADAPTIVE; > > Just curious; the way I read the SDM, we could leave this set, is that > correct? It needs to be cleared to get the basic record (which should be a common case) -Andi
