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The various sample types that are generated are based on the same SPE sample, just placed into different sample type bins. The same sample can be in multiple bins if it has flags set that cause it to be. Currently we're only applying the --itrace interval downsampling to the instruction bin, which means that the sample would appear in one bin but not another if it was skipped due to downsampling. I don't thing anyone would want or expect this, so make this behave consistently by applying the downsampling before generating any sample. You might argue that the "instructions" interval type doesn't make sense to apply to "memory" sample types because it would be skipping every n memory samples, rather than every n instructions. ut the downsampling was already not an instruction interval even for the instruction samples. SPE has a hardware based sampling interval, and the instruction interval was just a convenient way to specify further downsampling. This is hinted at in the warning message shown for intervals greater than 1. This makes SPE diverge from trace technologies like Intel PT and Arm Coresight. In those cases instruction samples can be reduced but all branches are still emitted. This makes sense there, because branches form a complete execution history, and asking to skip branches every n instructions doesn't really make sense. But for SPE, as mentioned above, downsampling the instruction samples already wasn't consistent with trace technologies so we ended up with some middle ground that had no benefit. Now it's possible to reduce the volume of samples in all groups and samples won't be missing from one group but present in another. Reviewed-by: Leo Yan <leo.yan@arm.com> Signed-off-by: James Clark <james.clark@linaro.org> Tested-by: Leo Yan <leo.yan@arm.com> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Ben Gainey <Ben.Gainey@arm.com> Cc: George Wort <George.Wort@arm.com> Cc: Graham Woodward <Graham.Woodward@arm.com> Cc: Ian Rogers <irogers@google.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: John Garry <john.g.garry@oracle.com> Cc: Leo Yan <leo.yan@linux.dev> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Michael Williams <Michael.Williams@arm.com> Cc: Mike Leach <mike.leach@linaro.org> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Will Deacon <will@kernel.org> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> |
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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.