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Re: [PATCH v3 2/5] perf/sdt: Add SDT events into a cache


On 10/22/2014 10:11 AM, Namhyung Kim wrote:

On Fri, 10 Oct 2014 16:28:24 +0530, Hemant Kumar wrote:

This patch adds a new sub-command to perf : sdt-cache.
sdt-cache command can be used to add SDT events.
When user invokes "perf sdt-cache add <file-name>", a hash table/list is
created named as file_hash list. A typical entry in a file_hash table looks
like:

                 file hash      file_sdt_ent     file_sdt_ent
                 |---------|   ---------------   -------------
                 | hlist ==|===|=>file_list =|===|=>file_list=|==..
     key = 644 =>|         |   | sbuild_id   |   | sbuild_id  |
                 |---------|   | name        |   | name       |
                 |         |   | sdt_list    |   | sdt_list   |
     key = 645 =>| hlist   |   |   ||        |   |    ||      |
                 |---------|   ---------------   --------------
                     ||            ||                 || Connected to SDT notes
                           ---------------
                           |  note_list  |
                           |  name       |sdt_note
                           |  provider   |
                           -----||--------
                   connected to other SDT notes

Each entry of the file_hash table is an hlist which connects to file_list
in file_sdt_ent. file_sdt_ent is allocated per file whenever a file is
mapped to file_hash list. File name serves as the key to this hash table.
If a file is added to this hash list, a file_sdt_ent is allocated and a
list of SDT events in that file is created and assigned to sdt_list of
file_sdt_ent.

Example usage :
# ./perf sdt-cache --add /home/user_app

     4 events added for /home/user_app

# ./perf sdt-cache --add /lib64/libc.so.6

     8 events added for /usr/lib64/libc-2.16.so

Signed-off-by: Hemant Kumar <hemant@linux.vnet.ibm.com>

[SNIP]

+static int file_hash_list__remove(struct hash_table *file_hash,
+				   const char *target)
+{
+	struct file_sdt_ent *fse;
+	struct hlist_head *ent_head;
+	struct list_head *sdt_head;
+	struct hlist_node *tmp1;
+	char *res_path;
+	int key, nr_del = 0;
+
+	res_path = realpath(target, NULL);
+	if (!res_path)
+		return -ENOMEM;
+
+	key = get_hash_key(target);
+	ent_head = &file_hash->ent[key];
+
+	/* Got the file hash entry */
+	hlist_for_each_entry_safe(fse, tmp1, ent_head, file_list) {
+		sdt_head = &fse->sdt_list;
+		if (strcmp(res_path, fse->name))
+			continue;
+
+		/* Got the file list entry, now start removing */
+		nr_del = cleanup_sdt_note_list(sdt_head);
+		hlist_del(&fse->file_list);
+		list_del(&fse->sdt_list);

It seems you don't need to call list_del() here.  And what about just
calling cleanup_sdt_note_list(&fse->sdt_list) instead?


Yeah, will remove this.




+		free(fse);
+	}
+	free(res_path);
+	return nr_del;
+}

[SNIP]

+static int sdt_note__read(char *data, struct list_head *sdt_list)
+{
+	struct sdt_note *sn;
+	char *tmp, *ptr, delim[2];
+	int ret = -EBADF, val;
+
+	/* Initialize the delimiter with DELIM */
+	delim[0] = DELIM;

What about delim[1] then?



It should be '\0' here, will initialize it.


+	sn = malloc(sizeof(*sn));
+	if (!sn) {
+		ret = -ENOMEM;
+		goto out;
+	}
+	INIT_LIST_HEAD(&sn->note_list);
+
+	/* Provider name */
+	ptr = strtok_r(data, delim, &tmp);
+	if (!ptr)
+		goto out;
+	sn->provider = strdup(ptr);
+	if (!sn->provider) {
+		ret = -ENOMEM;
+		goto out;
+	}
+	/* Marker name */
+	ptr = strtok_r(NULL, delim, &tmp);
+	if (!ptr)
+		goto out;
+	sn->name = strdup(ptr);
+	if (!sn->name) {
+		ret = -ENOMEM;
+		goto out;
+	}
+	/* Location */
+	ptr = strtok_r(NULL, delim, &tmp);
+	if (!ptr)
+		goto out;
+	val = sscanf(ptr, "%lx", &sn->addr.a64[0]);
+	if (val == EOF)
+		goto out;
+	/* Sempahore */
+	ptr = strtok_r(NULL, delim, &tmp);
+	if (!ptr)
+		goto out;
+	val = sscanf(ptr, "%lx", &sn->addr.a64[2]);
+	if (val == EOF)
+		goto out;
+	/* Add to the SDT list */
+	list_add(&sn->note_list, sdt_list);
+	ret = 0;
+out:
+	return ret;
+}
+
+/**
+ * file_hash_list__populate: Fill up the file hash table
+ * @file_hash: empty file hash table
+ * @cache: FILE * to read from
+ *
+ * Parse @cache for file_name and its SDT events.
+ * The format of the cache is :
+ *
+ * file_name:build_id\n
+ * provider:marker:location:semaphore\n

You seem forgot to add a file delimiter before new file.

       :\n

+ * file_name:build_id\n
+ * ...

Anyway IMHO it's bit uncomfortable.  How about changing the format same
as it dumps?  A line starts with '%' is a sdt description, otherwise
file info:

file_name1:build_id\n
%provide:marker1:location:semaphore\n
%provide:marker2:location:semaphore\n
%...
file_name2:build_id\n
%...

And we can deal with it by usual fgets/getline and strtok.

Oh, it's just a suggestion..


No problem. Will change the format to above.




+ *
+ * Parse according to the above format. Find out the file_name and build_id
+ * first and then use sdt_note__read() to parse the SDT note info.
+ * Find out the hash key from the file_name and use that to add this new
+ * entry to file hash.
+ */
+static int file_hash_list__populate(struct hash_table *file_hash, FILE *cache)
+{
+	struct file_sdt_ent *fse;
+	int key, val, ret = -EBADF;
+	char data[2 * PATH_MAX], *ptr, *tmp;
+
+	for (val = fscanf(cache, "%s", data); val != EOF;
+	     val = fscanf(cache, "%s", data)) {
+		fse = malloc(sizeof(*fse));
+		if (!fse) {
+			ret = -ENOMEM;
+			break;
+		}
+		INIT_LIST_HEAD(&fse->sdt_list);
+		INIT_HLIST_NODE(&fse->file_list);
+
+		/* First line is file name and build id */
+		ptr = strtok_r(data, ":", &tmp);
+		if (!ptr)
+			break;
+		strcpy(fse->name, ptr);
+		ptr = strtok_r(NULL, ":", &tmp);
+		if (!ptr)
+			break;
+		strcpy(fse->sbuild_id, ptr);
+
+		/* Now, try to get the SDT notes for that file */
+		while ((fscanf(cache, "%s", data)) != EOF) {
+			if (!strcmp(data, ":"))
+				break;
+			ret = sdt_note__read(data, &fse->sdt_list);
+			if (ret < 0)
+				goto out;
+		}
+		key = get_hash_key(fse->name);
+		hlist_add_head(&fse->file_list, &file_hash->ent[key]);
+		ret = 0;
+	}
+out:
+	return ret;
+}
+
+/**
+ * file_hash_list__init: Initializes the file hash list
+ * @file_hash: empty file_hash
+ *
+ * Initializes the ent's of file_hash and opens the cache file.

What is the ent's?


Hash entries. :) Will change to that to entries.


+ * To look for the cache file, look into the directory in HOME env variable.
+ */
+static int file_hash_list__init(struct hash_table *file_hash)
+{
+	FILE *cache;
+	int i, ret = 0;
+	char sdt_cache_path[MAXPATHLEN], *val;

s/MAXPATHLEN/PATH_MAX/ ?


Ok, for consistency, will change it to PATH_MAX.


+
+	for (i = 0; i < SDT_HASH_SIZE; i++)
+		INIT_HLIST_HEAD(&file_hash->ent[i]);
+
+	val = getenv("HOME");
+	if (val)
+		snprintf(sdt_cache_path, MAXPATHLEN-1, "%s/%s/%s",
+			 val, SDT_CACHE_DIR, SDT_FILE_CACHE);

Then you can use scnprintf(sdt_cache_path, sizeof(sdt_cache_path), ...).


Ok.




+	else {
+		pr_err("Error: Couldn't get user's home directory\n");
+		ret = -1;
+		goto out;
+	}
+
+	cache = fopen(sdt_cache_path, "r");
+	if (cache == NULL)
+		goto out;
+
+	/* Populate the hash list */
+	ret = file_hash_list__populate(file_hash, cache);
+	fclose(cache);
+out:
+	return ret;
+}
+
+/**
+ * file_hash_list__cleanup: Frees up all the space taken by file_hash list
+ * @file_hash: file_hash table
+ */
+static void file_hash_list__cleanup(struct hash_table *file_hash)
+{
+	struct file_sdt_ent *file_pos;
+	struct list_head *sdt_head;
+	struct hlist_head *ent_head;
+	struct hlist_node *tmp;
+	int i;
+
+	/* Go through all the entries */
+	for (i = 0; i < SDT_HASH_SIZE; i++) {
+		ent_head = &file_hash->ent[i];
+
+		hlist_for_each_entry_safe(file_pos, tmp, ent_head, file_list) {
+			sdt_head = &file_pos->sdt_list;
+
+			/* Cleanup the corresponding SDT notes' list */
+			cleanup_sdt_note_list(sdt_head);
+			hlist_del(&file_pos->file_list);
+			list_del(&file_pos->sdt_list);

Ditto.  Don't call list_del() but call cleanup_sdt_note_list directly.



Sure.


+			free(file_pos);
+		}
+	}
+}
+
+
+/**
+ * add_to_hash_list: add an entry to file_hash_list
+ * @file_hash: file hash table
+ * @target: file name
+ *
+ * Finds out the build_id of @target, checks if @target is already present
+ * in file hash list. If not present, delete any stale entries with this
+ * file name (i.e., entries matching this file name but having older
+ * build ids). And then, adds the file entry to file hash list and also
+ * updates the SDT events in the event hash list.
+ */
+static int add_to_hash_list(struct hash_table *file_hash, const char *target)
+{
+	struct file_info *file;
+	int ret = -EBADF;
+	u8 build_id[BUILD_ID_SIZE];
+
+	LIST_HEAD(sdt_notes);
+
+	file = malloc(sizeof(*file));
+	if (!file)
+		return -ENOMEM;
+
+	file->name = realpath(target, NULL);
+	if (!file->name) {
+		pr_err("%s: Bad file name\n", target);
+		goto out;
+	}
+
+	symbol__elf_init();

No need to call symbol__elf_init() here since we already called it in
cmd_sdt_cache().


Yeah, my bad. Will remove it.




+	if (filename__read_build_id(file->name, &build_id,
+				    sizeof(build_id)) < 0) {
+		pr_err("Couldn't read build-id in %s\n", file->name);
+		sdt_err(ret, file->name);
+		goto out;
+	}
+	build_id__sprintf(build_id, sizeof(build_id), file->sbuild_id);
+
+	/* File entry already exists ?*/
+	if (file_hash_list__entry_exists(file_hash, file)) {
+		pr_err("Error: SDT events for %s already exist\n",
+		       file->name);
+		ret = 0;
+		goto out;
+	}
+
+	/*
+	 * This should remove any stale entries (if any) from the file hash.
+	 * Stale entries will have the same file name but different build ids.
+	 */
+	ret = file_hash_list__remove(file_hash, file->name);
+	if (ret < 0)
+		goto out;
+	ret = get_sdt_note_list(&sdt_notes, file->name);
+	if (ret < 0)
+		sdt_err(ret, target);
+	/* Add the entry to file hash list */
+	ret = file_hash_list__add(file_hash, &sdt_notes, file);
+out:
+	free(file->name);
+	free(file);
+	return ret;
+}

[SNIP]

+static int flush_hash_list_to_cache(struct hash_table *file_hash)
+{
+	FILE *cache;
+	int ret;
+	struct stat buf;
+	char sdt_cache_path[MAXPATHLEN], sdt_dir[MAXPATHLEN], *val;
+
+	val = getenv("HOME");
+	if (val) {
+		snprintf(sdt_dir, MAXPATHLEN-1, "%s/%s", val, SDT_CACHE_DIR);
+		snprintf(sdt_cache_path, MAXPATHLEN-1, "%s/%s",
+			 sdt_dir, SDT_FILE_CACHE);

Ditto.  s/MAXPATHLEN/PATH_MAX/g and use scnprintf().

Thanks,
Namhyung



+	} else {
+		pr_err("Error: Couldn't get the user's home directory\n");
+		ret = -1;
+		goto out_err;
+	}
+	ret = stat(sdt_dir, &buf);
+	if (ret) {
+		ret = mkdir(sdt_dir, buf.st_mode);
+		if (ret) {
+			pr_err("Error: Couldn't create %s\n", sdt_dir);
+			goto out_err;
+		}
+	}
+
+	cache = fopen(sdt_cache_path, "w");
+	if (!cache) {
+		pr_err("Error in creating %s file\n", sdt_cache_path);
+		ret = -errno;
+		goto out_err;
+	}
+
+	file_hash_list__flush(file_hash, cache);
+	fclose(cache);
+out_err:
+	return ret;
+}


Thanks a lot for reviewing the patch.

--
Thanks,
Hemant Kumar
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