Messages in this thread | | | Date | Wed, 24 Jan 2018 11:17:21 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH V5 4/8] perf/x86/intel/uncore: add new data structures for free running counters |
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On Tue, Jan 23, 2018 at 10:00:58PM +0000, Liang, Kan wrote: > > On Fri, Jan 19, 2018 at 12:24:17PM -0800, Andi Kleen wrote: > > > > Oh, think a bit more. > > > > I think we cannot do the same thing as we did for CPU PMU's fixed > > counters. > > > > > > > > The counters here are free running counters. They cannot be start/stop. > > > > > > Yes free running counter have completely different semantics. They > > > need a separate event code. > > > > The only thing that matters is if they count the same thing or not. > > > > Hi Peter, > > There is NO event available on the GPs, that is exactly the same as > the free-running counters. > > For example, the BW free-running counters count the requests associated > with writes and completions. > The most similar events on the GPs are DATA_REQ_{OF,BY}_CPU.* events. > Except that some of their sub-events count requests which not completions. > There are also other minor differences. > So we don't have alternative events for the free-running counters. > I think we have to use 0xff.
OK, but explicitly mention this as the reason for having to invent event codes. Them being fixed purpose or free running isn't a valid reason for that.
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