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When the PAI events ALL_CRYPTO or ALL_NNPA are created for system wide sampling, all PAI counters are monitored. On each process schedule out, the values of all PAI counters are investigated. Non-zero values are saved in the event's ring buffer as raw data. This scheme expects the start value of each counter to be reset to zero after each read operation performed by the PAI PMU device driver. This allows for only one active event at any one time as it relies on the start value of counters to be reset to zero. Create a save area for each installed PAI XXXX_ALL event and save all PAI counter values in this save area. Instead of clearing the PAI counter lowcore area to zero after each read operation, copy them from the lowcore area to the event's save area at process schedule out time. The delta of each PAI counter is calculated by subtracting the old counter's value stored in the event's save area from the current value stored in the lowcore area. With this scheme, mulitple events of the PAI counters XXXX_ALL can be handled at the same time. This will be addressed in a follow-on patch. Signed-off-by: Thomas Richter <tmricht@linux.ibm.com> Acked-by: Sumanth Korikkar <sumanthk@linux.ibm.com> Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
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 Restructured Text 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.