Messages in this thread | | | From | Yang Shi <> | Date | Wed, 29 Mar 2023 16:25:24 -0700 | Subject | Re: [BUG] perf: No samples found when using kcore + coresight |
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On Wed, Mar 29, 2023 at 9:08 AM James Clark <james.clark@arm.com> wrote: > > > > On 14/03/2023 00:36, Leo Yan wrote: > > On Mon, Mar 13, 2023 at 11:15:44AM -0700, Yang Shi wrote: > > > > [...] > > > >>> Just a quick summary, here we have two issues: > >>> > >>> - With command: > >>> perf record -e cs_etm/@tmc_etf63/k --kcore --per-thread \ > >>> -- taskset --cpu-list 1 uname", > >>> > >>> perf doesn't enable "text poke" attribution. > >> > >> No, it enables "text poke" and perf fails to decode coresight trace > >> data too. It doesn't matter whether "--kcore" is after or before "-e > >> cs/etm/@tmc_etf63/k". > > > > Understand now. Thanks for correction, if so we can ignore this one. > > > > Leo > > To me it looks like it's only --per-thread and --kcore together that > cause the issue. I can't see if that was mentioned previously in this > thread.
If "--pre-thread" is not passed in, perf record failed with "failed to mmap with 12 (Cannot allocate memory)". Sorry for not mentioning this in the first place. I was quite focused on --kcore and didn't realize they may be related.
> > If it is --per-thread that's causing the issue then I think I have an > idea why it might be. There are some assumptions and different paths > taken in decoding in that mode that aren't correct. It causes some other > issues to do with ordering and timestamps as well and I wanted to fix it > previously. I wouldn't say that the text-poke change has caused a > regression, as decoding in this mode was always a bit buggy. > > Maybe this is another reason to fix it properly.
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