linux-kernel - Re: [PATCH v2 3/3] perf lock: Print the number of lost entries for BPF

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Date:   Mon, 26 Sep 2022 10:05:29 +0200
From:   Jiri Slaby <jirislaby@...nel.org>
To:     Namhyung Kim <namhyung@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>
Cc:     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 v2 3/3] perf lock: Print the number of lost entries for
 BPF

Hi,

On 02. 08. 22, 21:10, Namhyung Kim wrote:
> Like the normal perf lock contention output, it'd print the number of
> lost entries for BPF if exists or -v option is passed.  Currently it
> uses BROKEN_CONTENDED stat for the lost count (due to full stack maps).
...
> --- a/tools/perf/util/bpf_skel/lock_contention.bpf.c
> +++ b/tools/perf/util/bpf_skel/lock_contention.bpf.c
...
> @@ -73,6 +73,9 @@ int enabled;
>   int has_cpu;
>   int has_task;
>   
> +/* error stat */
> +unsigned long lost;

I don't know how all this is generated into lock_contention.skel.h. But 
I believe this patch breaks perf build on 32bit:
> [  375s] In file included from util/bpf_lock_contention.c:13:
> [  375s] util/bpf_skel/lock_contention.skel.h: In function 'lock_contention_bpf__assert':
> [  375s] util/bpf_skel/lock_contention.skel.h:537:9: error: static assertion failed: "unexpected size of \'lost\'"
> [  375s]   537 |         _Static_assert(sizeof(s->bss->lost) == 8, "unexpected size of 'lost'");
> [  375s]       |         ^~~~~~~~~~~~~~

Should the above (and below too) be __u64?

> --- 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_nr_entries;
> +	unsigned long lost;

thanks,
-- 
js
suse labs