powerpc/perf/vpa-dtl: Add support to capture DTL data in aux buffer

vpa dtl pmu has one hrtimer added per vpa-dtl pmu thread. When the
hrtimer expires, in the timer handler, code is added to save the DTL
data to perf event record via vpa_dtl_capture_aux() function.
The DTL (Dispatch Trace Log) contains information
about dispatch/preempt, enqueue time etc. We directly copy the DTL
buffer data as part of auxiliary buffer. Data will be written to
disk only when the allocated buffer is full.

By this approach, all the DTL data will be present as-is in the
perf.data. The data will be post-processed in perf tools side when doing
perf report/perf script and this will avoid time taken to create samples
in the kernel space.

To corelate each DTL entry with other events across CPU's, we need to
map timebase from "struct dtl_entry" which phyp provides with boot
timebase. This also needs timebase frequency. Define "struct boottb_freq"
to save these details.

Added changes to capture the Dispatch Trace Log details to AUX buffer
in vpa_dtl_dump_sample_data(). Boot timebase and frequency needs to be
saved only at once, added field to indicate this as part of
"vpa_pmu_buf" structure.

perf_aux_output_begin: This function is called before writing to AUX
area. This returns the pointer to aux area private structure, ie
"struct vpa_pmu_buf". The function obtains the output handle
(used in perf_aux_output_end). when capture completes in
vpa_dtl_capture_aux(), call perf_aux_output_end() to commit the recorded
data. perf_aux_output_end() is called to move the aux->head of
"struct perf_buffer" to indicate size of data in aux buffer.
aux_tail will be moved in perf tools side when writing the data from
aux buffer to perf.data file in disk.

It is responsiblity of PMU driver to make sure data is copied between
perf_aux_output_begin and perf_aux_output_end.

Signed-off-by: Athira Rajeev <atrajeev@linux.ibm.com>
Tested-by: Tejas Manhas <tejas05@linux.ibm.com>
Tested-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20250915102947.26681-6-atrajeev@linux.ibm.com

0 files changed, 0 insertions, 0 deletions