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2de8b6dd5a
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 |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.