Hi Peter, On Wed, Sep 6, 2017 at 1:40 AM, Peter Zijlstra <pet...@infradead.org> wrote: > 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.
Sure, that sounds fine to me. I dropped the last 2 events from a repost of the series since we can add that in (combined preempt and irq) at a later time using similar methods as you're suggesting. thanks, -Joel
