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Commit ce533d7c authored by Jin Qian's avatar Jin Qian Committed by Amit Pundir
Browse files

ANDROID: uid_sys_stats: reduce update_io_stats overhead 



Replaced read_lock with rcu_read_lock to reduce time that preemption
is disabled.

Added a function to update io stats for specific uid and moved
hash table lookup, user_namespace out of loops.

Bug: 37319300
Change-Id: I2b81b5cd3b6399b40d08c3c14b42cad044556970
Signed-off-by: default avatarJin Qian <jinqian@google.com>
parent 3291cd6f

drivers/misc/uid_sys_stats.c

+51 −10
Original line number Diff line number Diff line
@@ -235,28 +235,28 @@ static void clean_uid_io_last_stats(struct uid_entry *uid_entry, 
	io_last->fsync -= task->ioac.syscfs;

}



static void update_io_stats_locked(void)

static void update_io_stats_all_locked(void)

{

	struct uid_entry *uid_entry;

	struct task_struct *task, *temp;

	struct io_stats *io_bucket, *io_curr, *io_last;

	struct user_namespace *user_ns = current_user_ns();

	unsigned long bkt;



	BUG_ON(!rt_mutex_is_locked(&uid_lock));

	uid_t uid;



	hash_for_each(hash_table, bkt, uid_entry, hash)

		memset(&uid_entry->io[UID_STATE_TOTAL_CURR], 0,

			sizeof(struct io_stats));



	read_lock(&tasklist_lock);

	rcu_read_lock();

	do_each_thread(temp, task) {

		uid_entry = find_or_register_uid(from_kuid_munged(

			current_user_ns(), task_uid(task)));

		uid = from_kuid_munged(user_ns, task_uid(task));

		uid_entry = find_or_register_uid(uid);

		if (!uid_entry)

			continue;

		add_uid_io_curr_stats(uid_entry, task);

	} while_each_thread(temp, task);

	read_unlock(&tasklist_lock);

	rcu_read_unlock();



	hash_for_each(hash_table, bkt, uid_entry, hash) {

		io_bucket = &uid_entry->io[uid_entry->state];
@@ -279,6 +279,47 @@ static void update_io_stats_locked(void) 
	}

}



static void update_io_stats_uid_locked(uid_t target_uid)

{

	struct uid_entry *uid_entry;

	struct task_struct *task, *temp;

	struct io_stats *io_bucket, *io_curr, *io_last;

	struct user_namespace *user_ns = current_user_ns();



	uid_entry = find_or_register_uid(target_uid);

	if (!uid_entry)

		return;



	memset(&uid_entry->io[UID_STATE_TOTAL_CURR], 0,

		sizeof(struct io_stats));



	rcu_read_lock();

	do_each_thread(temp, task) {

		if (from_kuid_munged(user_ns, task_uid(task)) != target_uid)

			continue;

		add_uid_io_curr_stats(uid_entry, task);

	} while_each_thread(temp, task);

	rcu_read_unlock();



	io_bucket = &uid_entry->io[uid_entry->state];

	io_curr = &uid_entry->io[UID_STATE_TOTAL_CURR];

	io_last = &uid_entry->io[UID_STATE_TOTAL_LAST];



	io_bucket->read_bytes +=

		io_curr->read_bytes - io_last->read_bytes;

	io_bucket->write_bytes +=

		io_curr->write_bytes - io_last->write_bytes;

	io_bucket->rchar += io_curr->rchar - io_last->rchar;

	io_bucket->wchar += io_curr->wchar - io_last->wchar;

	io_bucket->fsync += io_curr->fsync - io_last->fsync;



	io_last->read_bytes = io_curr->read_bytes;

	io_last->write_bytes = io_curr->write_bytes;

	io_last->rchar = io_curr->rchar;

	io_last->wchar = io_curr->wchar;

	io_last->fsync = io_curr->fsync;

}



static int uid_io_show(struct seq_file *m, void *v)

{

	struct uid_entry *uid_entry;
@@ -286,7 +327,7 @@ static int uid_io_show(struct seq_file *m, void *v) 


	rt_mutex_lock(&uid_lock);



	update_io_stats_locked();

	update_io_stats_all_locked();



	hash_for_each(hash_table, bkt, uid_entry, hash) {

		seq_printf(m, "%d %llu %llu %llu %llu %llu %llu %llu %llu %llu %llu\n",
@@ -361,7 +402,7 @@ static ssize_t uid_procstat_write(struct file *file, 
		return count;

	}



	update_io_stats_locked();

	update_io_stats_uid_locked(uid);



	uid_entry->state = state;
@@ -399,7 +440,7 @@ static int process_notifier(struct notifier_block *self, 
	uid_entry->utime += utime;

	uid_entry->stime += stime;



	update_io_stats_locked();

	update_io_stats_uid_locked(uid);

	clean_uid_io_last_stats(uid_entry, task);



exit: