linux-kernel - Re: [PATCH v3] perf stat: Fix wrong skipping for per-die aggregation

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Date:   Mon, 4 Jan 2021 11:15:04 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Jin Yao <yao.jin@...ux.intel.com>
Cc:     acme@...nel.org, jolsa@...nel.org, peterz@...radead.org,
        mingo@...hat.com, alexander.shishkin@...ux.intel.com,
        Linux-kernel@...r.kernel.org, ak@...ux.intel.com,
        kan.liang@...el.com, yao.jin@...el.com, ying.huang@...el.com
Subject: Re: [PATCH v3] perf stat: Fix wrong skipping for per-die aggregation

On Fri, Dec 25, 2020 at 09:04:09AM +0800, Jin Yao wrote:

SNIP

>  void update_stats(struct stats *stats, u64 val)
> @@ -275,16 +276,39 @@ void evlist__save_aggr_prev_raw_counts(struct evlist *evlist)
>  
>  static void zero_per_pkg(struct evsel *counter)
>  {
> -	if (counter->per_pkg_mask)
> -		memset(counter->per_pkg_mask, 0, cpu__max_cpu());
> +	struct hashmap_entry *entry;
> +	size_t bkt;
> +
> +	if (counter->per_pkg_mask) {
> +		hashmap__for_each_entry(counter->per_pkg_mask, entry, bkt) {
> +			bool *used = (bool *)entry->value;
> +
> +			*used = false;
> +		}
> +	}
> +}
> +
> +static size_t id_hash(const void *key, void *ctx __maybe_unused)
> +{
> +	int socket = (int64_t)key >> 32;
> +
> +	return socket;
> +}
> +
> +static bool id_equal(const void *key1, const void *key2,
> +		     void *ctx __maybe_unused)
> +{
> +	return (int64_t)key1 == (int64_t)key2;
>  }

please use more descriptive names, pkg_id_hash/pkg_id_equal or such

>  
>  static int check_per_pkg(struct evsel *counter,
>  			 struct perf_counts_values *vals, int cpu, bool *skip)
>  {
> -	unsigned long *mask = counter->per_pkg_mask;
> +	struct hashmap *mask = counter->per_pkg_mask;
>  	struct perf_cpu_map *cpus = evsel__cpus(counter);
> -	int s;
> +	int s, d, ret;
> +	uint64_t key;
> +	bool *used;
>  
>  	*skip = false;
>  
> @@ -295,7 +319,7 @@ static int check_per_pkg(struct evsel *counter,
>  		return 0;
>  
>  	if (!mask) {
> -		mask = zalloc(cpu__max_cpu());
> +		mask = hashmap__new(id_hash, id_equal, NULL);
>  		if (!mask)
>  			return -ENOMEM;
>  
> @@ -317,7 +341,32 @@ static int check_per_pkg(struct evsel *counter,
>  	if (s < 0)
>  		return -1;
>  
> -	*skip = test_and_set_bit(s, mask) == 1;
> +	/*
> +	 * On multi-die system, 0 < die_id < 256. On no-die system, die_id = 0.
> +	 * We use hashmap(socket, die) to check the used socket+die pair.
> +	 */
> +	d = cpu_map__get_die(cpus, cpu, NULL).die;
> +	if (d < 0)
> +		return -1;
> +
> +	key = (uint64_t)s << 32 | (d & 0xff);
> +	if (hashmap__find(mask, (void *)key, (void **)&used)) {
> +		if (*used)
> +			*skip = true;
> +		*used = true;
> +	} else {
> +		used = zalloc(sizeof(*used));
> +		if (!used)
> +			return -1;

hum, what's the point of having extra bool value? once the
item is in the hashtab, we have the answer

I think you can add item to hashtab with '1' value and get
rid of that bool allocation

zero_per_pkg will be just removing all items from hashtab

jirka