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The bpf_get_kmem_cache() kfunc can return an address of the slab cache
(kmem_cache). As it has the name of the slab cache from the iterator,
we can use it to symbolize some dynamic kernel locks in a slab.
Before:
root@virtme-ng:/home/namhyung/project/linux# tools/perf/perf lock con -abl sleep 1
contended total wait max wait avg wait address symbol
2 3.34 us 2.87 us 1.67 us ffff9d7800ad9600 (mutex)
2 2.16 us 1.93 us 1.08 us ffff9d7804b992d8 (mutex)
4 1.37 us 517 ns 343 ns ffff9d78036e6e00 (mutex)
1 1.27 us 1.27 us 1.27 us ffff9d7804b99378 (mutex)
2 845 ns 599 ns 422 ns ffffffff9e1c3620 delayed_uprobe_lock (mutex)
1 845 ns 845 ns 845 ns ffffffff9da0b280 jiffies_lock (spinlock)
2 377 ns 259 ns 188 ns ffffffff9e1cf840 pcpu_alloc_mutex (mutex)
1 305 ns 305 ns 305 ns ffffffff9e1b4cf8 tracepoint_srcu_srcu_usage (mutex)
1 295 ns 295 ns 295 ns ffffffff9e1c0940 pack_mutex (mutex)
1 232 ns 232 ns 232 ns ffff9d7804b7d8d8 (mutex)
1 180 ns 180 ns 180 ns ffffffff9e1b4c28 tracepoint_srcu_srcu_usage (mutex)
1 165 ns 165 ns 165 ns ffffffff9da8b3a0 text_mutex (mutex)
After:
root@virtme-ng:/home/namhyung/project/linux# tools/perf/perf lock con -abl sleep 1
contended total wait max wait avg wait address symbol
2 1.95 us 1.77 us 975 ns ffff9d5e852d3498 &task_struct (mutex)
1 1.18 us 1.18 us 1.18 us ffff9d5e852d3538 &task_struct (mutex)
4 1.12 us 354 ns 279 ns ffff9d5e841ca800 &kmalloc-cg-512 (mutex)
2 859 ns 617 ns 429 ns ffffffffa41c3620 delayed_uprobe_lock (mutex)
3 691 ns 388 ns 230 ns ffffffffa41c0940 pack_mutex (mutex)
3 421 ns 164 ns 140 ns ffffffffa3a8b3a0 text_mutex (mutex)
1 409 ns 409 ns 409 ns ffffffffa41b4cf8 tracepoint_srcu_srcu_usage (mutex)
2 362 ns 239 ns 181 ns ffffffffa41cf840 pcpu_alloc_mutex (mutex)
1 220 ns 220 ns 220 ns ffff9d5e82b534d8 &signal_cache (mutex)
1 215 ns 215 ns 215 ns ffffffffa41b4c28 tracepoint_srcu_srcu_usage (mutex)
Note that the name starts with '&' sign for slab objects to inform they
are dynamic locks. It won't give the accurate lock or type names but
it's still useful. We may add type info to the slab cache later to get
the exact name of the lock in the type later.
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Ian Rogers <irogers@google.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Chun-Tse Shao <ctshao@google.com>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Kees Cook <kees@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Song Liu <song@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Link: https://lore.kernel.org/r/20241220060009.507297-4-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.