linux-kernel - Re: [PATCH 3/3] perf lock: Print lost entries at the end

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Message-ID: <YulipRqJZ7oYVWD/@kernel.org>
Date:   Tue, 2 Aug 2022 14:45:09 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Jiri Olsa <jolsa@...nel.org>, Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Ian Rogers <irogers@...gle.com>,
        linux-perf-users@...r.kernel.org, Will Deacon <will@...nel.org>,
        Waiman Long <longman@...hat.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Song Liu <songliubraving@...com>,
        Blake Jones <blakejones@...gle.com>
Subject: Re: [PATCH 3/3] perf lock: Print lost entries at the end

Em Tue, Aug 02, 2022 at 12:35:11AM -0700, Namhyung Kim escreveu:
> Like the normal perf lock report output, it'd print bad stats at the end
> if exists or -v option is passed.  Currently it uses BROKEN_CONTENDED
 stat for the lost count (due to full stack maps).

"Print the number of lost entries in verbose mode"?
 
>   $ sudo perf lock con -a -b -m 128 sleep 5
>   ...
>   === output for debug===
> 
>   bad: 43, total: 14903
>   bad rate: 0.29 %
>   histogram of events caused bad sequence
>       acquire: 0
>      acquired: 0
>     contended: 43
>       release: 0
> 
> Signed-off-by: Namhyung Kim <namhyung@...nel.org>
> ---
>  tools/perf/builtin-lock.c                      | 8 +++++++-
>  tools/perf/util/bpf_lock_contention.c          | 6 ++++--
>  tools/perf/util/bpf_skel/lock_contention.bpf.c | 9 +++++++--
>  tools/perf/util/lock-contention.h              | 1 +
>  4 files changed, 19 insertions(+), 5 deletions(-)
> 
> diff --git a/tools/perf/builtin-lock.c b/tools/perf/builtin-lock.c
> index e32fdcd497e0..8065f0268e55 100644
> --- a/tools/perf/builtin-lock.c
> +++ b/tools/perf/builtin-lock.c
> @@ -1471,8 +1471,11 @@ static void print_contention_result(void)
>  		pr_info("  %10s   %s\n\n", "type", "caller");
>  
>  	bad = total = 0;
> +	if (use_bpf)
> +		bad = bad_hist[BROKEN_CONTENDED];
> +
>  	while ((st = pop_from_result())) {
> -		total++;
> +		total += use_bpf ? st->nr_contended : 1;
>  		if (st->broken)
>  			bad++;
>  
> @@ -1686,6 +1689,9 @@ static int __cmd_contention(int argc, const char **argv)
>  
>  		lock_contention_stop();
>  		lock_contention_read(&con);
> +
> +		/* abuse bad hist stats for lost entries */
> +		bad_hist[BROKEN_CONTENDED] = con.lost;
>  	} else {
>  		err = perf_session__process_events(session);
>  		if (err)
> diff --git a/tools/perf/util/bpf_lock_contention.c b/tools/perf/util/bpf_lock_contention.c
> index 26128e5bb659..65f51cc25236 100644
> --- a/tools/perf/util/bpf_lock_contention.c
> +++ b/tools/perf/util/bpf_lock_contention.c
> @@ -16,7 +16,7 @@ static struct lock_contention_bpf *skel;
>  
>  /* should be same as bpf_skel/lock_contention.bpf.c */
>  struct lock_contention_key {
> -	u32 stack_id;
> +	s32 stack_id;
>  };
>  
>  struct lock_contention_data {
> @@ -110,7 +110,7 @@ int lock_contention_stop(void)
>  int lock_contention_read(struct lock_contention *con)
>  {
>  	int fd, stack;
> -	u32 prev_key, key;
> +	s32 prev_key, key;
>  	struct lock_contention_data data;
>  	struct lock_stat *st;
>  	struct machine *machine = con->machine;
> @@ -119,6 +119,8 @@ int lock_contention_read(struct lock_contention *con)
>  	fd = bpf_map__fd(skel->maps.lock_stat);
>  	stack = bpf_map__fd(skel->maps.stacks);
>  
> +	con->lost = skel->bss->lost;
> +
>  	prev_key = 0;
>  	while (!bpf_map_get_next_key(fd, &prev_key, &key)) {
>  		struct map *kmap;
> diff --git a/tools/perf/util/bpf_skel/lock_contention.bpf.c b/tools/perf/util/bpf_skel/lock_contention.bpf.c
> index 67d46533e518..9e8b94eb6320 100644
> --- a/tools/perf/util/bpf_skel/lock_contention.bpf.c
> +++ b/tools/perf/util/bpf_skel/lock_contention.bpf.c
> @@ -12,7 +12,7 @@
>  #define MAX_ENTRIES  10240
>  
>  struct contention_key {
> -	__u32 stack_id;
> +	__s32 stack_id;
>  };
>  
>  struct contention_data {
> @@ -27,7 +27,7 @@ struct tstamp_data {
>  	__u64 timestamp;
>  	__u64 lock;
>  	__u32 flags;
> -	__u32 stack_id;
> +	__s32 stack_id;
>  };
>  
>  /* callstack storage  */
> @@ -73,6 +73,9 @@ int enabled;
>  int has_cpu;
>  int has_task;
>  
> +/* error stat */
> +unsigned long lost;
> +
>  static inline int can_record(void)
>  {
>  	if (has_cpu) {
> @@ -116,6 +119,8 @@ int contention_begin(u64 *ctx)
>  	pelem->flags = (__u32)ctx[1];
>  	pelem->stack_id = bpf_get_stackid(ctx, &stacks, BPF_F_FAST_STACK_CMP);
>  
> +	if (pelem->stack_id < 0)
> +		lost++;
>  	return 0;
>  }
>  
> diff --git a/tools/perf/util/lock-contention.h b/tools/perf/util/lock-contention.h
> index b09fd6eb978a..d9fc5f076567 100644
> --- a/tools/perf/util/lock-contention.h
> +++ b/tools/perf/util/lock-contention.h
> @@ -113,6 +113,7 @@ struct lock_contention {
>  	struct machine *machine;
>  	struct hlist_head *result;
>  	unsigned long map_len;
> +	unsigned long lost;
>  };
>  
>  #ifdef HAVE_BPF_SKEL
> -- 
> 2.37.1.455.g008518b4e5-goog

-- 

- Arnaldo