On Tue, 29 Oct 2013, Peter Zijlstra wrote: > On Tue, Oct 29, 2013 at 04:28:10AM +0000, Will Deacon wrote: > > > > I can CC LKML on ARM perf patches if you think it will help, but all PMU > > backend patches go via their respective arch trees afaict. > > Just those that change user visible semantics that are shared between > archs I suppose :-)
I suppose it is hard to know what's commonly shared. I hadn't realized that the IOC_PERIOD stuff was arch specific code, I would have thought it was common code. Since there isn't a perf-specific list CCing LKML might be the answer even though it sometimes adds to the noise. I think the Power people CC all their PMU related patches to LKML and it has made them easier to find and review. > We could start by making all archs do the same thing again; but yes > ideally we'd move some of it into generic code. Not entirely sure how > that will work out though, there's a reason its in per-arch code :/ > > > Vince, what would you prefer to do here? as with most of thes things there isn't really a good answer. It turns out in the end that PAPI isn't bit by this one, because instead of using PERF_EVENT_IOC_PERIOD when the period is changed, PAPI just tears down all the perf_events and re-sets them up from scratch with the new period. This is probably because PERF_EVENT_IOC_PERIOD was broken until 2.6.36. It is true the current behavior is unexpected. What was the logic behind deferring to the next overflow for the update? Was it a code simplicity thing? Or were there hardware reasons behind it? Definitely when an event is stopped, it makes more sense for PERF_EVENT_IOC_PERIOD to take place immediately. I'm not sure what happens if we try to use it on a running event, especially if we've already passed the new period value. Vince -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
