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The powerpc cpuid information includes chip revision information. Changes between chip revisions are usually minor bug fixes and usually do not affect the operation of the performance monitoring hardware. The original mapfile.csv matching requires enumerating every possible cpuid string. When a new minor chip revision is produced a new entry has to be added to the mapfile.csv and the code recompiled to allow perf to have the implementation specific perf events for this new minor revision. For users of various distibutions of Linux having to wait for a new release of the kernel's perf tool to be built with these trivial patches is inconvenient. Using regular expressions rather than exactly string matching of the entire cpuid string allows developers to write mapfile.csv files that do not require patches and recompiles for each of these minor version changes. If special cases need to be made for some particular versions, they can be placed earlier in the mapfile.csv file before the more general matches. Signed-off-by: William Cohen <wcohen@redhat.com> Tested-by: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Michael Petlan <mpetlan@redhat.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Shriya <shriyak@linux.vnet.ibm.com> Link: http://lkml.kernel.org/r/20171204145728.16792-1-wcohen@redhat.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.