On Tue, Jun 19, 2018 at 01:47:25PM +0300, Alexander Shishkin wrote: > On Thu, Jun 14, 2018 at 10:20:22PM +0200, Peter Zijlstra wrote:
> > More yuck... > > > > You rreally should not be calling these pmu::methods, they're meant to > > be used from _interrupt_ not NMI context. Using them like this is asking > > for tons of trouble. > > Right, the SW stuff may then race with event_function_call() stuff. Hmm. > For the HW stuff, I'm hoping that some kind of a sleight of hand may > suffice. Let me think some more. I currently don't see how the SW driven snapshot can ever work, see my comment on the last patch. > > Why can't you just snapshot the current location and let the thing > > 'run' ? > > Because the buffer will overwrite itself and the location will be useless. Not if it's large enough ;-) > We don't write the AUX data out in this 'mode' at all, only the samples, > which allows for much less data in the resulting perf.data, less work for > the consumer, less IO bandwidth etc, and as a bonus, no AUX-related > interrupts. > > But actually, even to snapshot the location we need to stop the event. Maybe new methods that should only be called from NMI context?
