On 2019/10/9 19:09, Tan Xiaojun wrote: > On 2019/10/9 17:48, James Clark wrote: >> Hi Xiaojun, >> >>> By the way, you mentioned before that you want the spe event to be in the >>> form of "event:pp" like pebs. Is that the whole framework should be made >>> similar to pebs? Or is it just a modification to the command format? >> >> We're currently still investigating if it makes sense to modify the Perf >> event open syscall to use SPE when the "precise_ip" attribute is set. And >> then synthesize samples using the SPE data when available. This would keep >> the syscall interface more consistent between architectures. >> >> And if tools other than Perf want more precise data, they don't have to be >> aware of SPE or any of the implementation defined details of it. For example >> the 'data source' encoding can be different from one micro architecture to >> the next. The kernel is probably the best place to handle this. >> >> At the moment, every tool that wants to use the Perf syscall to get precise >> data on ARM would have to be aware of SPE and implement their own decoding. >> > > Hi James, > > What do you mean when the user specifies "event:pp", if the SPE is available, > configure and record the spe data directly via the perf event open syscall? > (perf.data itself is the same as using -e arm_spe_0//xxx?)
I mean, for the perf record, if the user does not add ":pp" to these events, the original process is taken, and if ":pp" is added, the spe process is taken. Xiaojun. > > OK. If I have not misunderstood, I think I know how to do it. > Thank you. > >>> For the former, this may be a bit difficult. For the latter, there is >>> currently no modification to the record part, so "-c -F, etc." is only for >>> instructions rather than events, so it may be misunderstood by users. >>> >>> So I haven't figured out how to do. What do you think of this? >> >> I think the patch at the moment is a good start to make SPE more accessible. >> And the changes I mentioned above wouldn't change the fact that the raw SPE >> data would still be available via the SPE PMU. So I think continuing with >> the patch as-is for now is the best idea. >> > > Yes. I agree. > > Xiaojun. > >> >> James >> >> >
