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Normally, for cycle-acccurate mode, IPC values are an exact number of instructions and cycles. Due to the granularity of timestamps, that happens only when a CYC packet correlates to the event. Support the itrace 'A' option, to use instead, the number of cycles associated with the current timestamp. This provides IPC information for every change of timestamp, but at the expense of accuracy. Due to the granularity of timestamps, the actual number of cycles increases even though the cycles reported does not. The number of instructions is known, but if IPC is reported, cycles can be too low and so IPC is too high. Note that inaccuracy decreases as the period of sampling increases i.e. if the number of cycles is too low by a small amount, that becomes less significant if the number of cycles is large. Furthermore, it can be used in conjunction with dlfilter-show-cycles.so to provide higher granularity cycle information. Reviewed-by: Andi Kleen <ak@linux.intel.com> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com> Cc: Jiri Olsa <jolsa@redhat.com> Link: https://lore.kernel.org/r/20211027080334.365596-4-adrian.hunter@intel.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.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.