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07d85ba9d0
Hundreds of "read LOST count failed" error messages may be displayed,
when the below command is launched.
perf record -e '{cpu/mem-loads-aux/,cpu/event=0xcd,umask=0x1/}:S' -a
According to the commit 89e3106fa2 ("libperf: Handle read format
in perf_evsel__read()"), the PERF_FORMAT_GROUP is only available for
the leader. However, the record__read_lost_samples() goes through every
entry of an evlist, which includes both leader and member. The member
event errors out and triggers the error message. Since there may be
hundreds of CPUs on a server, the message will be printed hundreds of
times, which is very annoying.
The message itself is correct, but the pr_err is a overkill. Other error
messages in the record__read_lost_samples() are all pr_debug. To make
the output format consistent, change the pr_err("read LOST count
failed\n"); to pr_debug("read LOST count failed\n");.
User can still get the message via -v option.
Fixes: e3a23261ad ("perf record: Read and inject LOST_SAMPLES events")
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20230301150413.27011-1-kan.liang@linux.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.