Hi Stephane,
I am testing an implementation of libpfm4, and ran into some curious behavior
with the plm field in the perf_event_attr structure. The code makes it appear
to be intentional, but I thought I'd run this by you to see if it's what you
had
intended.
If I specify an event, such as PM_RUN_CYC:i, and I don't specify any u,k, or h
modifiers, none of the exclude_* bits in the perf_events attribute record get
set. This seems ok; users may want to have events counted in all privilege
levels by default.
However, if I specify "PM_RUN_CYC:i:k=0", saying I don't want kernel samples, I
actually get all samples, because of this code:
if (perf_attrs.plm) {
hw->exclude_user = !(perf_attrs.plm & PFM_PLM3);
hw->exclude_kernel = !(perf_attrs.plm & PFM_PLM0);
hw->exclude_hv = !(perf_attrs.plm & PFM_PLMH);
}
perf_attrs.plm is set to zero, if I set k=0. If I were using this interface,
I'd probably want hw->exclude_kernel to be set to 1.
Do you agree? Should the behavior be changed?
Regards,
- Corey
Corey Ashford
Software Engineer
IBM Linux Technology Center, Linux Toolchain
Beaverton, OR
503-578-3507
cjash...@us.ibm.com
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