Re: [PATCH V3 02/17] perf header: Support CPU PMU capabilities

[Arnaldo Carvalho de Melo]

Em Fri, Mar 13, 2020 at 11:33:04AM -0700, kan.liang@xxxxxxxxxxxxxxx escreveu:
> From: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
> 
> To stitch LBR call stack, the max LBR information is required. So the
> CPU PMU capabilities information has to be stored in perf header.
> 
> Add a new feature HEADER_CPU_PMU_CAPS for CPU PMU capabilities.
> Retrieve all CPU PMU capabilities, not just max LBR information.
> 
> Add variable max_branches to facilitate future usage.
> 
> Reviewed-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> Signed-off-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
> ---
>  .../Documentation/perf.data-file-format.txt   |  16 +++
>  tools/perf/util/env.h                         |   3 +
>  tools/perf/util/header.c                      | 110 ++++++++++++++++++
>  tools/perf/util/header.h                      |   1 +
>  4 files changed, 130 insertions(+)
> 
> diff --git a/tools/perf/Documentation/perf.data-file-format.txt b/tools/perf/Documentation/perf.data-file-format.txt
> index b0152e1095c5..b6472e463284 100644
> --- a/tools/perf/Documentation/perf.data-file-format.txt
> +++ b/tools/perf/Documentation/perf.data-file-format.txt
> @@ -373,6 +373,22 @@ struct {
>  Indicates that trace contains records of PERF_RECORD_COMPRESSED type
>  that have perf_events records in compressed form.
>  
> +	HEADER_CPU_PMU_CAPS = 28,
> +
> +	A list of cpu PMU capabilities. The format of data is as below.
> +
> +struct {
> +	u32 nr_cpu_pmu_caps;
> +	{
> +		char	name[];
> +		char	value[];
> +	} [nr_cpu_pmu_caps]
> +};
> +
> +
> +Example:
> + cpu pmu capabilities: branches=32, max_precise=3, pmu_name=icelake
> +
>  	other bits are reserved and should ignored for now
>  	HEADER_FEAT_BITS	= 256,
>  
> diff --git a/tools/perf/util/env.h b/tools/perf/util/env.h
> index 11d05ae3606a..d286d478b4d8 100644
> --- a/tools/perf/util/env.h
> +++ b/tools/perf/util/env.h
> @@ -48,6 +48,7 @@ struct perf_env {
>  	char			*cpuid;
>  	unsigned long long	total_mem;
>  	unsigned int		msr_pmu_type;
> +	unsigned int		max_branches;
>  
>  	int			nr_cmdline;
>  	int			nr_sibling_cores;
> @@ -57,12 +58,14 @@ struct perf_env {
>  	int			nr_memory_nodes;
>  	int			nr_pmu_mappings;
>  	int			nr_groups;
> +	int			nr_cpu_pmu_caps;
>  	char			*cmdline;
>  	const char		**cmdline_argv;
>  	char			*sibling_cores;
>  	char			*sibling_dies;
>  	char			*sibling_threads;
>  	char			*pmu_mappings;
> +	char			*cpu_pmu_caps;
>  	struct cpu_topology_map	*cpu;
>  	struct cpu_cache_level	*caches;
>  	int			 caches_cnt;
> diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
> index acbd046bf95c..ce29321a4e1d 100644
> --- a/tools/perf/util/header.c
> +++ b/tools/perf/util/header.c
> @@ -1395,6 +1395,39 @@ static int write_compressed(struct feat_fd *ff __maybe_unused,
>  	return do_write(ff, &(ff->ph->env.comp_mmap_len), sizeof(ff->ph->env.comp_mmap_len));
>  }
>  
> +static int write_cpu_pmu_caps(struct feat_fd *ff,
> +			      struct evlist *evlist __maybe_unused)
> +{
> +	struct perf_pmu_caps *caps = NULL;
> +	struct perf_pmu *cpu_pmu;
> +	int nr_caps;
> +	int ret;
> +
> +	cpu_pmu = perf_pmu__find("cpu");

please combine decl + assign:

+	struct perf_pmu *cpu_pmu = perf_pmu__find("cpu");

> +	if (!cpu_pmu)
> +		return -ENOENT;
> +
> +	nr_caps = perf_pmu__caps_parse(cpu_pmu);
> +	if (nr_caps < 0)
> +		return nr_caps;
> +
> +	ret = do_write(ff, &nr_caps, sizeof(nr_caps));
> +	if (ret < 0)
> +		return ret;
> +
> +	while ((caps = perf_pmu__scan_caps(cpu_pmu, caps))) {

Why can't you play use list_for_each_entry() here and remove that perf_pmu__scan_caps()?

> +		ret = do_write_string(ff, caps->name);
> +		if (ret < 0)
> +			return ret;
> +
> +		ret = do_write_string(ff, caps->value);
> +		if (ret < 0)
> +			return ret;
> +	}
> +
> +	return ret;
> +}
> +
>  static void print_hostname(struct feat_fd *ff, FILE *fp)
>  {
>  	fprintf(fp, "# hostname : %s\n", ff->ph->env.hostname);
> @@ -1809,6 +1842,28 @@ static void print_compressed(struct feat_fd *ff, FILE *fp)
>  		ff->ph->env.comp_level, ff->ph->env.comp_ratio);
>  }
>  
> +static void print_cpu_pmu_caps(struct feat_fd *ff, FILE *fp)
> +{
> +	const char *delimiter = "# cpu pmu capabilities: ";
> +	char *str;
> +	u32 nr_caps;
> +
> +	nr_caps = ff->ph->env.nr_cpu_pmu_caps;

ditto

> +	if (!nr_caps) {
> +		fprintf(fp, "# cpu pmu capabilities: not available\n");
> +		return;
> +	}
> +
> +	str = ff->ph->env.cpu_pmu_caps;
> +	while (nr_caps--) {
> +		fprintf(fp, "%s%s", delimiter, str);
> +		delimiter = ", ";
> +		str += strlen(str) + 1;
> +	}
> +
> +	fprintf(fp, "\n");
> +}
> +
>  static void print_pmu_mappings(struct feat_fd *ff, FILE *fp)
>  {
>  	const char *delimiter = "# pmu mappings: ";
> @@ -2846,6 +2901,60 @@ static int process_compressed(struct feat_fd *ff,
>  	return 0;
>  }
>  
> +static int process_cpu_pmu_caps(struct feat_fd *ff,
> +				void *data __maybe_unused)
> +{
> +	char *name, *value;
> +	struct strbuf sb;
> +	u32 nr_caps;
> +
> +	if (do_read_u32(ff, &nr_caps))
> +		return -1;
> +
> +	if (!nr_caps) {
> +		pr_debug("cpu pmu capabilities not available\n");
> +		return 0;
> +	}
> +
> +	ff->ph->env.nr_cpu_pmu_caps = nr_caps;
> +
> +	if (strbuf_init(&sb, 128) < 0)
> +		return -1;
> +
> +	while (nr_caps--) {
> +		name = do_read_string(ff);
> +		if (!name)
> +			goto error;
> +
> +		value = do_read_string(ff);
> +		if (!value)
> +			goto free_name;
> +
> +		if (strbuf_addf(&sb, "%s=%s", name, value) < 0)
> +			goto free_value;
> +
> +		/* include a NULL character at the end */
> +		if (strbuf_add(&sb, "", 1) < 0)
> +			goto free_value;
> +
> +		if (!strcmp(name, "branches"))
> +			ff->ph->env.max_branches = atoi(value);
> +
> +		free(value);
> +		free(name);
> +	}
> +	ff->ph->env.cpu_pmu_caps = strbuf_detach(&sb, NULL);
> +	return 0;
> +
> +free_value:
> +	free(value);
> +free_name:
> +	free(name);
> +error:
> +	strbuf_release(&sb);
> +	return -1;
> +}
> +
>  #define FEAT_OPR(n, func, __full_only) \
>  	[HEADER_##n] = {					\
>  		.name	    = __stringify(n),			\
> @@ -2903,6 +3012,7 @@ const struct perf_header_feature_ops feat_ops[HEADER_LAST_FEATURE] = {
>  	FEAT_OPR(BPF_PROG_INFO, bpf_prog_info,  false),
>  	FEAT_OPR(BPF_BTF,       bpf_btf,        false),
>  	FEAT_OPR(COMPRESSED,	compressed,	false),
> +	FEAT_OPR(CPU_PMU_CAPS,	cpu_pmu_caps,	false),
>  };
>  
>  struct header_print_data {
> diff --git a/tools/perf/util/header.h b/tools/perf/util/header.h
> index 840f95cee349..650bd1c7a99b 100644
> --- a/tools/perf/util/header.h
> +++ b/tools/perf/util/header.h
> @@ -43,6 +43,7 @@ enum {
>  	HEADER_BPF_PROG_INFO,
>  	HEADER_BPF_BTF,
>  	HEADER_COMPRESSED,
> +	HEADER_CPU_PMU_CAPS,
>  	HEADER_LAST_FEATURE,
>  	HEADER_FEAT_BITS	= 256,
>  };
> -- 
> 2.17.1
> 

-- 

- Arnaldo