Messages in this thread | | | Date | Thu, 19 Aug 2010 09:32:18 +0100 | From | Matt Fleming <> | Subject | Re: [RFC PATCH 0/3] perf: show package power consumption in perf |
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On Thu, Aug 19, 2010 at 04:31:54PM +0800, Zhang Rui wrote: > On Thu, 2010-08-19 at 15:54 +0800, Matt Fleming wrote: > > On Thu, Aug 19, 2010 at 11:28:17AM +0800, Lin Ming wrote: > > > On Wed, 2010-08-18 at 20:41 +0800, Matt Fleming wrote: > > > > > > > > I had a quick look over the patches and Peter is right - the group > > > > events stuff would probably fit quite well here. Unfortunately, due to > > > > holidays and things, I haven't been able to get them finished > > > > yet. I'll get on that ASAP. > > > > > > Hi, Matt > > > > > > What's the "group events stuff"? > > > Is there some discussion on LKML or elsewhere I can have a look at? > > > > > > Thanks, > > > Lin Ming > > > > The relevant information can be found here in this thread, > > http://lkml.org/lkml/2010/8/4/174. I'm working on some patches for > > this but they're not finished yet. I can probably get something to > > show by next week. > > > > The discussion started because the performance counters on SH do not > > generate an interrupt on overflow, so we need to periodically sample > > them. Am I correct in thinking that the energy counters also do not > > generate an interrupt on overflow and that's why you wrote the event > > as a software event? > > right. > > BTW, I'm not quite familiar with perf tool, and now I'm wondering if the > periodically sample is needed. > because IMO, .start is invoked every time the process is scheduled in, > and .stop is invoked when it's scheduled out. It seems that we just need > to read the energy consumed in .start and .stop, and update the counter > in .stop, right?
How big is the hardware counter? The problem comes when the process is scheduled in and runs for a long time, e.g. so long that the energy hardware counter wraps. This is why it's necessary to periodically sample the counter.
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