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It needs callstacks for two reasons:
* for stack aggregation mode, the map key is the stack id and it can
also show the full stack traces when -v is used
* for other aggregation modes, the stack filter can be used to limit
lock contentions from known call paths
The -v option is meaningful (in terms of stack trace) only for stack
aggregation mode, so it should not set the save_callstack for other
mode like with -t or -l options.
I've noticed this with the following command line:
$ sudo ./perf lock con -ablv -E 3 -M 16 -- ./perf bench sched messaging
...
contended total wait max wait avg wait address symbol
88 4.59 ms 108.07 us 52.13 us ffff935757f46ec0 (spinlock)
33 905.22 us 73.67 us 27.43 us ffff935757f41700 (spinlock)
28 703.69 us 79.28 us 25.13 us ffff938a3d9b0c80 rq_lock (spinlock)
=== output for debug ===
bad: 12272, total: 12421
bad rate: 98.80 %
histogram of failure reasons
task: 8285
stack: 3987 <---------- here
time: 0
data: 0
It should not have any failure on stacks since it doesn't use it.
No functional change intended.
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Hao Luo <haoluo@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <song@kernel.org>
Cc: bpf@vger.kernel.org
Link: https://lore.kernel.org/r/20230406210611.1622492-2-namhyung@kernel.org
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.