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Linux kernel source tree
4afdc00c37
The control knobs set before loading BPF programs should be declared as
'const volatile' so that it can be optimized by the BPF core.
Committer testing:
root@x1:~# perf lock contention --use-bpf
contended total wait max wait avg wait type caller
5 31.57 us 14.93 us 6.31 us mutex btrfs_delayed_update_inode+0x43
1 16.91 us 16.91 us 16.91 us rwsem:R btrfs_tree_read_lock_nested+0x1b
1 15.13 us 15.13 us 15.13 us spinlock btrfs_getattr+0xd1
1 6.65 us 6.65 us 6.65 us rwsem:R btrfs_tree_read_lock_nested+0x1b
1 4.34 us 4.34 us 4.34 us spinlock process_one_work+0x1a9
root@x1:~#
root@x1:~# perf trace -e bpf --max-events 10 perf lock contention --use-bpf
0.000 ( 0.013 ms): :2948281/2948281 bpf(cmd: 36, uattr: 0x7ffd5f12d730, size: 8) = -1 EOPNOTSUPP (Operation not supported)
0.024 ( 0.120 ms): :2948281/2948281 bpf(cmd: PROG_LOAD, uattr: 0x7ffd5f12d460, size: 148) = 16
0.158 ( 0.034 ms): :2948281/2948281 bpf(cmd: PROG_LOAD, uattr: 0x7ffd5f12d520, size: 148) = 16
26.653 ( 0.154 ms): perf/2948281 bpf(cmd: PROG_LOAD, uattr: 0x7ffd5f12d3d0, size: 148) = 16
26.825 ( 0.014 ms): perf/2948281 bpf(uattr: 0x7ffd5f12d580, size: 80) = 16
87.924 ( 0.038 ms): perf/2948281 bpf(cmd: BTF_LOAD, uattr: 0x7ffd5f12d400, size: 40) = 16
87.988 ( 0.006 ms): perf/2948281 bpf(cmd: BTF_LOAD, uattr: 0x7ffd5f12d470, size: 40) = 16
88.019 ( 0.006 ms): perf/2948281 bpf(cmd: BTF_LOAD, uattr: 0x7ffd5f12d250, size: 40) = 16
88.029 ( 0.172 ms): perf/2948281 bpf(cmd: PROG_LOAD, uattr: 0x7ffd5f12d320, size: 148) = 17
88.217 ( 0.005 ms): perf/2948281 bpf(cmd: BTF_LOAD, uattr: 0x7ffd5f12d4d0, size: 40) = 16
root@x1:~#
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20240902200515.2103769-5-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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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.