On Mon, Dec 21, 2009 at 04:40:40PM +0100, Peter Zijlstra wrote: > I'm not really seeing the problem here... > > > perf_disable() <-- shut down the full pmu > > pmu->disable() <-- hey someone got removed (easy free the reg) > pmu->enable() <-- hey someone got added (harder, check constraints) > > hw_perf_group_sched_in() <-- hey a full group got added > (better than multiple ->enable) > > perf_enable() <-- re-enable pmu > > > So ->disable() is used to track freeing, ->enable is used to add > individual counters, check constraints etc.. > > hw_perf_group_sched_in() is used to optimize the full group enable. > > Afaict that is what power does (Paul?) and that should I think be > sufficient to track x86 as well.
That sounds right to me. > Since sched_in() is balanced with sched_out(), the ->disable() calls > should provide the required information as to the occupation of the pmu. > I don't see the need for more hooks. > > Paul, could you comment, since you did all this for power? On powerpc we maintain a list of currently enabled events in the arch code. Does x86 do that as well? If you have the list (or array) of events easily accessible, it's relatively easy to check whether the whole set is feasible at any point, without worrying about which events were recently added. The perf_event structure has a spot where the arch code can store which PMU register is used for that event, so you can easily optimize the case where the event doesn't move. Like you, I'm not seeing where the difficulty lies. Perhaps Stephane could give us a detailed example if he still thinks there's a difficulty. Paul. ------------------------------------------------------------------------------ This SF.Net email is sponsored by the Verizon Developer Community Take advantage of Verizon's best-in-class app development support A streamlined, 14 day to market process makes app distribution fast and easy Join now and get one step closer to millions of Verizon customers http://p.sf.net/sfu/verizon-dev2dev _______________________________________________ perfmon2-devel mailing list perfmon2-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/perfmon2-devel
