Commit 0c631ef0 authored by Namhyung Kim's avatar Namhyung Kim Committed by Arnaldo Carvalho de Melo
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perf lock contention: Resolve slab object name using BPF



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: default avatarNamhyung Kim <namhyung@kernel.org>
Acked-by: default avatarIan Rogers <irogers@google.com>
Tested-by: default avatarArnaldo 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: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent e2c4dc54
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