On Tue, Sep 05, 2017 at 09:35:11AM -0700, Joel Fernandes wrote: > On Mon, Sep 4, 2017 at 11:52 PM, Peter Zijlstra <pet...@infradead.org> wrote: > > On Mon, Sep 04, 2017 at 08:26:13PM -0700, Joel Fernandes wrote: > > > >> Apologies, I meant (without the "off"): > >> > >> subsystem: atomic_section > >> events: > >> irqs_disable > >> irqs_enable > >> preempt_disable > >> preempt_enable > >> > >> and additionally (similar to what my patch does): > >> preemptirq_enable > >> preemptirq_disable > >> > > > > What do you need the last for? > > The last 2 events above behave as 'disable' means either preempt or > irq got disabled, and 'enable' means *both* preempt and irq are > enabled (after either one of them was disabled). > > This has the advantage of not generating events when we're already in > an atomic section when using these events, for example acquiring spin > locks in an interrupt handler might increase the preempt count and > generate 'preempt_disable' events, but not preemptirq_disable events. > This has the effect of reducing the spam in the traces when all we > care about is being in an atomic section or not. These events happen a > lot so to conserve space in the trace buffer, the user may want to > just enable the latter 2 events. Does that sound Ok to you?
Hurm,... how about placing a filter on the other 4, such that we only emit the event on 0<->x state transitions? IIRC tracing already has filter bits and eBPF bits on that allow something like that. That avoids having to introduce more tracepoints and gets you the same results.
