Messages in this thread | | | Date | Mon, 10 Oct 2022 10:21:22 +0100 | Subject | Re: [PATCH] perf test: Fix test_arm_coresight.sh failures on Juno | From | James Clark <> |
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On 10/10/2022 08:41, Leo Yan wrote: > On Thu, Oct 06, 2022 at 04:11:05PM +0100, James Clark wrote: > > [...] > >>>> Before: >>>> >>>> sudo ./perf test coresight -vvv >>>> ... >>>> Recording trace with system wide mode >>>> Looking at perf.data file for dumping branch samples: >>>> Looking at perf.data file for reporting branch samples: >>>> Looking at perf.data file for instruction samples: >>>> CoreSight system wide testing: FAIL >>>> ... >>>> >>>> After: >>>> >>>> sudo ./perf test coresight -vvv >>>> ... >>>> Recording trace with system wide mode >>>> Looking at perf.data file for dumping branch samples: >>>> Looking at perf.data file for reporting branch samples: >>>> Looking at perf.data file for instruction samples: >>>> CoreSight system wide testing: PASS >>>> ... >>> >>> Since Arm Juno board has zero timestamp for CoreSight, I don't think >>> now arm_cs_etm.sh can really work on it. >>> >>> If we want to pass the test on Juno board, we need to add option >>> "--itrace=Zi1000i" for "perf report" and "perf script"; but seems >>> to me "--itrace=Z..." is not a general case for testing ... >> >> Unfortunately I now think that adding the Z option didn't improve >> anything in Coresight decoding other than removing the warning. I've >> never seen the zero timestamp issue on Juno though. I thought that was >> on some Qualcomm device? I'm not getting the warning on this test anyway. > > No, on my Juno-r2 board I can observe the timestamp is always zero > from CoreSight trace data, this is why everytime I must use > "--itrace=Zi1000i" for reporting results.
Ah I have r0 which could explain it. But it's good to know that r2 has that issue. I still wouldn't expect you to have to use the option though, because it should only make the warning go away.
> >> The problem is that timeless mode assumes per thread mode, and in per >> thread mode there is a separate buffer per thread, so the Coresight >> channel IDs are ignored. In systemwide mode the channel ID is important >> to know which CPU the trace came from. If this info is thrown away then >> not much works correctly. >> >> I plan to overhaul the whole decoder and remove all the assumptions >> about per-thread and timeless mode. It would be better if they were >> completely separate concepts. > > Okay, good to know this. > > [...] > >>> So here I am suspect that changing to "--itrace=i20i" can allow the test >>> to pass on Juno board. Could you confirm for this? >> >> On Juno: >> >> ./perf record -e cs_etm// -a -- ls >> >> With interval 20, 23 instruction samples are generated: >> >> ./perf report --stdio --itrace=i20i | egrep " +[0-9]+\.[0-9]+% +perf " >> | wc -l >> >> 23 >> >> With interval 1000, 0 are generated: >> >> ./perf report --stdio --itrace=i1000i | egrep " +[0-9]+\.[0-9]+% +perf >> " | wc -l >> >> Error: >> The perf.data data has no samples! >> 0 > > Thanks for confirmation. It's a bit weird that your Juno board doesn't > produce all zeros for timestamp packets. > >> I think the issue is that ls is quite quick to run, so not much trace is >> generated for Perf. And it just depends on the scheduling which is >> slightly different on Juno. I don't think it's a bug. On N1SDP there are >> only 134 samples generated with i1000i, so it could probably end up with >> a random run generating 0 there too. > > Agreed, changing to smaller interval makes sense for me. > > Reviewed-by: Leo Yan <leo.yan@linaro.org>
Thanks for the review Leo
> > Thanks, > Leo
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