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

[Hemant Kumar]

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@xxxxxxxxxxxxxxxxxx>
> [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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