Commit 806bce6a authored May 25, 2017 by Ganesh Mahendran Committed by Amit Pundir Dec 18, 2017

ANDROID: uid_sys_stats: check previous uid_entry before call find_or_register_uid



Theads in a process are stored in list struct task_struct->thread_group,
so it will be visited continiously in below loop:
do_each_thread(temp, task) {
    ...
} while_each_thread(temp, task);

I add some log in the loop, we can see below information:
[   65.033561] uid 1000, uid_entry ffffffc0f2761600
[   65.033567] uid 1000, uid_entry ffffffc0f2761600
[   65.033574] uid 1000, uid_entry ffffffc0f2761600
[   65.033581] uid 1000, uid_entry ffffffc0f2761600
[   65.033588] uid 1000, uid_entry ffffffc0f2761600
[   65.033595] uid 1000, uid_entry ffffffc0f2761600
[   65.033602] uid 1000, uid_entry ffffffc0f2761600
[   65.033609] uid 1000, uid_entry ffffffc0f2761600
[   65.033615] uid 1000, uid_entry ffffffc0f2761600
[   65.033622] uid 1000, uid_entry ffffffc0f2761600
[   65.033629] uid 1000, uid_entry ffffffc0f2761600
[   65.033637] uid 1000, uid_entry ffffffc0f2761600
[   65.033644] uid 1000, uid_entry ffffffc0f2761600
[   65.033651] uid 1000, uid_entry ffffffc0f2761600
[   65.033658] uid 1000, uid_entry ffffffc0f2761600
[   65.033665] uid 1000, uid_entry ffffffc0f2761600
[   65.033672] uid 1000, uid_entry ffffffc0f2761600
[   65.033680] uid 1000, uid_entry ffffffc0f2761600
[   65.033687] uid 1000, uid_entry ffffffc0f2761600
[   65.033694] uid 1000, uid_entry ffffffc0f2761600
[   65.033701] uid 1000, uid_entry ffffffc0f2761600
[   65.033708] uid 1000, uid_entry ffffffc0f2761600
[   65.033715] uid 1000, uid_entry ffffffc0f2761600
[   65.033722] uid 1000, uid_entry ffffffc0f2761600
[   65.033729] uid 1000, uid_entry ffffffc0f2761600
[   65.033736] uid 1000, uid_entry ffffffc0f2761600
[   65.033743] uid 1000, uid_entry ffffffc0f2761600
[   65.033750] uid 1000, uid_entry ffffffc0f2761600
[   65.033757] uid 1000, uid_entry ffffffc0f2761600
[   65.033763] uid 1000, uid_entry ffffffc0f2761600
[   65.033770] uid 1000, uid_entry ffffffc0f2761600
[   65.033777] uid 1000, uid_entry ffffffc0f2761600
[   65.033784] uid 1000, uid_entry ffffffc0f2761600
[   65.033791] uid 1000, uid_entry ffffffc0f2761600
[   65.033798] uid 1000, uid_entry ffffffc0f2761600

So we can check the previous uid_entry before calling find_or_register_uid
to save time.

Change-Id: I05ec1a1405a80c0a620cb4b4b2f6483dbfde7829
Signed-off-by: Ganesh Mahendran <opensource.ganesh@gmail.com>

parent df06c7f9

drivers/misc/uid_sys_stats.c

+6 −4

Original line number	Diff line number	Diff line
		@@ -95,7 +95,7 @@ static struct uid_entry *find_or_register_uid(uid_t uid)

		static int uid_cputime_show(struct seq_file m, void v)
		{
		struct uid_entry *uid_entry;
		struct uid_entry *uid_entry = NULL;
		struct task_struct task, temp;
		struct user_namespace *user_ns = current_user_ns();
		u64 utime;
		@@ -113,6 +113,7 @@ static int uid_cputime_show(struct seq_file m, void v)
		read_lock(&tasklist_lock);
		do_each_thread(temp, task) {
		uid = from_kuid_munged(user_ns, task_uid(task));
		if (!uid_entry \|\| uid_entry->uid != uid)
		uid_entry = find_or_register_uid(uid);
		if (!uid_entry) {
		read_unlock(&tasklist_lock);
		@@ -249,7 +250,7 @@ static void compute_uid_io_bucket_stats(struct io_stats *io_bucket,

		static void update_io_stats_all_locked(void)
		{
		struct uid_entry *uid_entry;
		struct uid_entry *uid_entry = NULL;
		struct task_struct task, temp;
		struct user_namespace *user_ns = current_user_ns();
		unsigned long bkt;
		@@ -262,6 +263,7 @@ static void update_io_stats_all_locked(void)
		rcu_read_lock();
		do_each_thread(temp, task) {
		uid = from_kuid_munged(user_ns, task_uid(task));
		if (!uid_entry \|\| uid_entry->uid != uid)
		uid_entry = find_or_register_uid(uid);
		if (!uid_entry)
		continue;