Commit d24c0144 authored by Namhyung Kim's avatar Namhyung Kim Committed by Arnaldo Carvalho de Melo
Browse files

perf lock contention: Show per-cpu rq_lock with address 



Using the BPF_PROG_RUN mechanism, we can run a raw_tp BPF program to
collect some semi-global locks like per-cpu locks.  Let's add runqueue
locks using bpf_per_cpu_ptr() helper.

  $ sudo ./perf lock con -abl -- sleep 1
   contended   total wait     max wait     avg wait            address   symbol

         248      3.25 ms     32.23 us     13.10 us   ffff8cc75cfd2940   siglock
          60    217.91 us      9.69 us      3.63 us   ffff8cc700061c00
           8     70.23 us     13.86 us      8.78 us   ffff8cc703629484
           4     56.32 us     35.81 us     14.08 us   ffff8cc78b66f778   mmap_lock
           4     16.70 us      5.18 us      4.18 us   ffff8cc7036a0684
           3      4.99 us      2.65 us      1.66 us   ffff8d053da30c80   rq_lock
           2      3.44 us      2.28 us      1.72 us   ffff8d053dcf0c80   rq_lock
           9      2.51 us       371 ns       278 ns   ffff8ccb92479440
           2      2.11 us      1.24 us      1.06 us   ffff8d053db30c80   rq_lock
           2      2.06 us      1.69 us      1.03 us   ffff8d053d970c80   rq_lock

Signed-off-by: default avatarNamhyung Kim <namhyung@kernel.org>
Cc: Boqun Feng <boqun.feng@gmail.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: Stephane Eranian <eranian@google.com>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will@kernel.org>
Cc: bpf@vger.kernel.org
Link: https://lore.kernel.org/r/20230313204825.2665483-2-namhyung@kernel.org


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 1811e827

tools/perf/util/bpf_lock_contention.c

+25 −2
Original line number Diff line number Diff line
@@ -151,6 +151,8 @@ int lock_contention_prepare(struct lock_contention *con) 
	skel->bss->needs_callstack = con->save_callstack;

	skel->bss->lock_owner = con->owner;



	bpf_program__set_autoload(skel->progs.collect_lock_syms, false);



	lock_contention_bpf__attach(skel);

	return 0;

}
@@ -198,14 +200,26 @@ static const char *lock_contention_get_name(struct lock_contention *con, 
	}



	if (con->aggr_mode == LOCK_AGGR_ADDR) {

		int lock_fd = bpf_map__fd(skel->maps.lock_syms);



		/* per-process locks set upper bits of the flags */

		if (flags & LCD_F_MMAP_LOCK)

			return "mmap_lock";

		if (flags & LCD_F_SIGHAND_LOCK)

			return "siglock";



		/* global locks with symbols */

		sym = machine__find_kernel_symbol(machine, key->lock_addr, &kmap);

		if (sym)

			name = sym->name;

		return name;

			return sym->name;



		/* try semi-global locks collected separately */

		if (!bpf_map_lookup_elem(lock_fd, &key->lock_addr, &flags)) {

			if (flags == LOCK_CLASS_RQLOCK)

				return "rq_lock";

		}



		return "";

	}



	/* LOCK_AGGR_CALLER: skip lock internal functions */
@@ -258,6 +272,15 @@ int lock_contention_read(struct lock_contention *con) 
		thread__set_comm(idle, "swapper", /*timestamp=*/0);

	}



	if (con->aggr_mode == LOCK_AGGR_ADDR) {

		DECLARE_LIBBPF_OPTS(bpf_test_run_opts, opts,

			.flags = BPF_F_TEST_RUN_ON_CPU,

		);

		int prog_fd = bpf_program__fd(skel->progs.collect_lock_syms);



		bpf_prog_test_run_opts(prog_fd, &opts);

	}



	/* make sure it loads the kernel map */

	map__load(maps__first(machine->kmaps));

tools/perf/util/bpf_skel/lock_contention.bpf.c

+31 −0
Original line number Diff line number Diff line
@@ -10,6 +10,9 @@ 
/* default buffer size */

#define MAX_ENTRIES  10240



/* for collect_lock_syms().  4096 was rejected by the verifier */

#define MAX_CPUS  1024



/* lock contention flags from include/trace/events/lock.h */

#define LCB_F_SPIN	(1U << 0)

#define LCB_F_READ	(1U << 1)
@@ -56,6 +59,13 @@ struct { 
	__uint(max_entries, MAX_ENTRIES);

} task_data SEC(".maps");



struct {

	__uint(type, BPF_MAP_TYPE_HASH);

	__uint(key_size, sizeof(__u64));

	__uint(value_size, sizeof(__u32));

	__uint(max_entries, 16384);

} lock_syms SEC(".maps");



struct {

	__uint(type, BPF_MAP_TYPE_HASH);

	__uint(key_size, sizeof(__u32));
@@ -384,4 +394,25 @@ int contention_end(u64 *ctx) 
	return 0;

}



extern struct rq runqueues __ksym;



SEC("raw_tp/bpf_test_finish")

int BPF_PROG(collect_lock_syms)

{

	__u64 lock_addr;

	__u32 lock_flag;



	for (int i = 0; i < MAX_CPUS; i++) {

		struct rq *rq = bpf_per_cpu_ptr(&runqueues, i);



		if (rq == NULL)

			break;



		lock_addr = (__u64)&rq->__lock;

		lock_flag = LOCK_CLASS_RQLOCK;

		bpf_map_update_elem(&lock_syms, &lock_addr, &lock_flag, BPF_ANY);

	}

	return 0;

}



char LICENSE[] SEC("license") = "Dual BSD/GPL";

tools/perf/util/bpf_skel/lock_data.h

+5 −0
Original line number Diff line number Diff line
@@ -36,4 +36,9 @@ enum lock_aggr_mode { 
	LOCK_AGGR_CALLER,

};



enum lock_class_sym {

	LOCK_CLASS_NONE,

	LOCK_CLASS_RQLOCK,

};



#endif /* UTIL_BPF_SKEL_LOCK_DATA_H */