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Date:   Sat, 2 Dec 2017 12:47:59 +0800
From:   "Jin, Yao" <yao.jin@...ux.intel.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     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
Subject: Re: [PATCH v5 10/12] perf util: Reuse thread_map__new_by_uid to
 enumerate threads from /proc



On 12/1/2017 10:44 PM, Arnaldo Carvalho de Melo wrote:
> Em Fri, Dec 01, 2017 at 06:57:34PM +0800, Jin Yao escreveu:
>> Perf already has a function thread_map__new_by_uid() which can
>> enumerate all threads from /proc by uid.
>>
>> This patch creates a static function enumerate_threads() which
>> reuses the common code in thread_map__new_by_uid() to enumerate
>> threads from /proc.
>>
>> The enumerate_threads() is shared by thread_map__new_by_uid()
>> and a new function thread_map__new_threads().
>>
>> The new function thread_map__new_threads() is called to enumerate
>> all threads from /proc.
>>
>> Signed-off-by: Jin Yao <yao.jin@...ux.intel.com>
>> ---
>>   tools/perf/tests/thread-map.c |  2 +-
>>   tools/perf/util/evlist.c      |  3 ++-
>>   tools/perf/util/thread_map.c  | 19 ++++++++++++++++---
>>   tools/perf/util/thread_map.h  |  3 ++-
>>   4 files changed, 21 insertions(+), 6 deletions(-)
>>
>> diff --git a/tools/perf/tests/thread-map.c b/tools/perf/tests/thread-map.c
>> index dbcb6a1..4de1939 100644
>> --- a/tools/perf/tests/thread-map.c
>> +++ b/tools/perf/tests/thread-map.c
>> @@ -105,7 +105,7 @@ int test__thread_map_remove(struct test *test __maybe_unused, int subtest __mayb
>>   	TEST_ASSERT_VAL("failed to allocate map string",
>>   			asprintf(&str, "%d,%d", getpid(), getppid()) >= 0);
>>   
>> -	threads = thread_map__new_str(str, NULL, 0);
>> +	threads = thread_map__new_str(str, NULL, 0, false);
>>   
>>   	TEST_ASSERT_VAL("failed to allocate thread_map",
>>   			threads);
>> diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
>> index 199bb82..05b8f2b 100644
>> --- a/tools/perf/util/evlist.c
>> +++ b/tools/perf/util/evlist.c
>> @@ -1102,7 +1102,8 @@ int perf_evlist__create_maps(struct perf_evlist *evlist, struct target *target)
>>   	struct cpu_map *cpus;
>>   	struct thread_map *threads;
>>   
>> -	threads = thread_map__new_str(target->pid, target->tid, target->uid);
>> +	threads = thread_map__new_str(target->pid, target->tid, target->uid,
>> +				      target->per_thread);
>>   
>>   	if (!threads)
>>   		return -1;
>> diff --git a/tools/perf/util/thread_map.c b/tools/perf/util/thread_map.c
>> index be0d5a7..5672268 100644
>> --- a/tools/perf/util/thread_map.c
>> +++ b/tools/perf/util/thread_map.c
>> @@ -92,7 +92,7 @@ struct thread_map *thread_map__new_by_tid(pid_t tid)
>>   	return threads;
>>   }
>>   
>> -struct thread_map *thread_map__new_by_uid(uid_t uid)
>> +static struct thread_map *enumerate_threads(uid_t uid)
>>   {
>>   	DIR *proc;
>>   	int max_threads = 32, items, i;
>> @@ -124,7 +124,7 @@ struct thread_map *thread_map__new_by_uid(uid_t uid)
>>   		if (stat(path, &st) != 0)
>>   			continue;
> 
> Look, for the case where you want all threads enumerated you will incur
> the above stat() cost for all of them and will not use it at all...
> 
> And new_threads() seems vague, I'm using the ter used by 'perf record'
> for system wide sampling, see the patch below:
> 
> diff --git a/tools/perf/util/thread_map.c b/tools/perf/util/thread_map.c
> index be0d5a736dea..79d11bd4543a 100644
> --- a/tools/perf/util/thread_map.c
> +++ b/tools/perf/util/thread_map.c
> @@ -92,7 +92,7 @@ struct thread_map *thread_map__new_by_tid(pid_t tid)
>   	return threads;
>   }
>   
> -struct thread_map *thread_map__new_by_uid(uid_t uid)
> +static struct thread_map *__thread_map__new_all_cpus(uid_t uid)
>   {
>   	DIR *proc;
>   	int max_threads = 32, items, i;
> @@ -113,7 +113,6 @@ struct thread_map *thread_map__new_by_uid(uid_t uid)
>   	while ((dirent = readdir(proc)) != NULL) {
>   		char *end;
>   		bool grow = false;
> -		struct stat st;
>   		pid_t pid = strtol(dirent->d_name, &end, 10);
>   
>   		if (*end) /* only interested in proper numerical dirents */
> @@ -121,11 +120,12 @@ struct thread_map *thread_map__new_by_uid(uid_t uid)
>   
>   		snprintf(path, sizeof(path), "/proc/%s", dirent->d_name);
>   
> -		if (stat(path, &st) != 0)
> -			continue;
> +		if (uid != UID_MAX) {
> +			struct stat st;
>   
> -		if (st.st_uid != uid)
> -			continue;
> +			if (stat(path, &st) != 0 || st.st_uid != uid)
> +				continue;
> +		}
>   
>   		snprintf(path, sizeof(path), "/proc/%d/task", pid);
>   		items = scandir(path, &namelist, filter, NULL);
> @@ -178,6 +178,16 @@ struct thread_map *thread_map__new_by_uid(uid_t uid)
>   	goto out_closedir;
>   }
>   
> +struct thread_map *thread_map__new_all_cpus(void)
> +{
> +	return __thread__new_all_cpus(UID_MAX);
> +}
> +
> +struct thread_map *thread_map__new_by_uid(uid_t uid)
> +{
> +	return __thread__new_all_cpus(uid);
> +}
> +
>   struct thread_map *thread_map__new(pid_t pid, pid_t tid, uid_t uid)
>   {
>   	if (pid != -1)
> diff --git a/tools/perf/util/thread_map.h b/tools/perf/util/thread_map.h
> index f15803985435..07a765fb22bb 100644
> --- a/tools/perf/util/thread_map.h
> +++ b/tools/perf/util/thread_map.h
> @@ -23,6 +23,7 @@ struct thread_map *thread_map__new_dummy(void);
>   struct thread_map *thread_map__new_by_pid(pid_t pid);
>   struct thread_map *thread_map__new_by_tid(pid_t tid);
>   struct thread_map *thread_map__new_by_uid(uid_t uid);
> +struct thread_map *thread_map__new_all_cpus(void);
>   struct thread_map *thread_map__new(pid_t pid, pid_t tid, uid_t uid);
>   struct thread_map *thread_map__new_event(struct thread_map_event *event);
>   
> 

It looks good, thanks Arnaldo!

Thanks
Jin Yao

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