Messages in this thread | | | Date | Mon, 30 Aug 2010 20:35:58 +0100 | From | Matt Fleming <> | Subject | Re: [RFC][PATCH 3/5] perf: Add hrtimer code for PMI-less hardware counters |
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On Mon, Aug 30, 2010 at 04:12:24PM +0200, Peter Zijlstra wrote: > On Mon, 2010-08-30 at 14:27 +0100, Matt Fleming wrote: > > > I'm lost. Is it possible to do this patch entirely in userspace? How do > > we periodically sample the counters if it's not being done in the > > kernel? > > perf_event_attr leader = { > .type = PERF_TYPE_SOFTWARE, > .config = PERF_COUNT_SW_TASK_CLOCK, > .sample_period = xxx, > .sample_type = PERF_SAMPLE_READ|..., > .read_format = PERF_FORMAT_GROUP, > }; > > perf_event_attr counter = { > .type = PERF_TYPE_HARDWARE, > .config = PERF_COUNT_HW_CPU_CYCLES, > }; > > leader_fd = sys_perf_event_open(&leader, pid, cpu, 0, 0); > counter_fd = sys_perf_event_open(&counter, pid, cpu, leader_fd, 0); > > Which gives you a group of 2 events, one software timer that samples, > one hardware counter that only counts.
Aha. OK, thanks! I'll respin this.
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