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When the Dispatch Trace Log data is collected along with other events like sched tracepoint events, it needs to be correlated and present interleaved along with these events. Perf events can be collected parallely across the CPUs. Hence it needs to be ensured events/dtl entries are processed in timestamp order. An auxtrace_queue is created for each CPU. Data within each queue is in increasing order of timestamp. Each auxtrace queue has a array/list of auxtrace buffers. When processing the auxtrace buffer, the data is mmapp'ed. All auxtrace queues is maintained in auxtrace heap. Each queue has a queue number and a timestamp. The queues are sorted/added to head based on the time stamp. So always the lowest timestamp (entries to be processed first) is on top of the heap. The auxtrace queue needs to be allocated and heap needs to be populated in the sorted order of timestamp. The queue needs to be filled with data only once via powerpc_vpadtl__update_queues() function. powerpc_vpadtl__setup_queues() iterates through all the entries to allocate and setup the auxtrace queue. To add to auxtrace heap, it is required to fetch the timebase of first entry for each of the queue. The first entry in the queue for VPA DTL PMU has the boot timebase, frequency details which are needed to get timestamp which is required to correlate with other events. The very next entry is the actual trace data that provides timestamp for occurrence of DTL event. Formula used to get the timestamp from dtl entry is: ((timbase from DTL entry - boot time) / frequency) * 1000000000 powerpc_vpadtl_decode() adds the boot time and frequency as part of powerpc_vpadtl_queue structure so that it can be reused. Each of the dtl_entry is of 48 bytes size. Sometimes it could happen that one buffer is only partially processed (if the timestamp of occurrence of another event is more than currently processed element in queue, it will move on to next event). In order to keep track of position of buffer, additional fields is added to powerpc_vpadtl_queue structure. Reviewed-by: Adrian Hunter <adrian.hunter@intel.com> 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> Cc: Aboorva Devarajan <aboorvad@linux.ibm.com> Cc: Aditya Bodkhe <Aditya.Bodkhe1@ibm.com> Cc: Hari Bathini <hbathini@linux.vnet.ibm.com> Cc: Ian Rogers <irogers@google.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Madhavan Srinivasan <maddy@linux.ibm.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Shrikanth Hegde <sshegde@linux.ibm.com> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> |
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| lib | ||
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| README | ||
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.