android-5.4/ANDROID-cpufreq-times-optimize-proc-files.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Connor O'Brien <connoro@google.com>
Date: Wed, 20 Feb 2019 12:17:48 -0800
Subject: ANDROID: cpufreq: times: optimize proc files

The majority of the time spent reading /proc/uid_time_in_state is due
to seq_printf calls. Use the faster seq_put_* variations instead.

Also skip empty hash buckets in uid_seq_next for a further performance
improvement.

Bug: 111216804
Bug: 127641090
Test: Read /proc/uid_time_in_state and confirm output is sane
Test: Compare read times to confirm performance improvement
Change-Id: If8783b498ed73d2ddb186a49438af41ac5ab9957
Signed-off-by: Connor O'Brien <connoro@google.com>
---
 drivers/cpufreq/cpufreq_times.c | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/drivers/cpufreq/cpufreq_times.c b/drivers/cpufreq/cpufreq_times.c
index 42420c5e1e6f..2883d675b1eb 100644
--- a/drivers/cpufreq/cpufreq_times.c
+++ b/drivers/cpufreq/cpufreq_times.c
@@ -193,10 +193,12 @@ static void *uid_seq_start(struct seq_file *seq, loff_t *pos)
 
 static void *uid_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 {
-	(*pos)++;
+	do {
+		(*pos)++;
 
-	if (*pos >= HASH_SIZE(uid_hash_table))
-		return NULL;
+		if (*pos >= HASH_SIZE(uid_hash_table))
+			return NULL;
+	} while (hlist_empty(&uid_hash_table[*pos]));
 
 	return &uid_hash_table[*pos];
 }
@@ -220,7 +222,8 @@ static int uid_time_in_state_seq_show(struct seq_file *m, void *v)
 				if (freqs->freq_table[i] ==
 				    CPUFREQ_ENTRY_INVALID)
 					continue;
-				seq_printf(m, " %d", freqs->freq_table[i]);
+				seq_put_decimal_ull(m, " ",
+						    freqs->freq_table[i]);
 			}
 		}
 		seq_putc(m, '\n');
@@ -229,13 +232,16 @@ static int uid_time_in_state_seq_show(struct seq_file *m, void *v)
 	rcu_read_lock();
 
 	hlist_for_each_entry_rcu(uid_entry, (struct hlist_head *)v, hash) {
-		if (uid_entry->max_state)
-			seq_printf(m, "%d:", uid_entry->uid);
+		if (uid_entry->max_state) {
+			seq_put_decimal_ull(m, "", uid_entry->uid);
+			seq_putc(m, ':');
+		}
 		for (i = 0; i < uid_entry->max_state; ++i) {
+			u64 time;
 			if (freq_index_invalid(i))
 				continue;
-			seq_printf(m, " %lu", (unsigned long)nsec_to_clock_t(
-					   uid_entry->time_in_state[i]));
+			time = nsec_to_clock_t(uid_entry->time_in_state[i]);
+			seq_put_decimal_ull(m, " ", time);
 		}
 		if (uid_entry->max_state)
 			seq_putc(m, '\n');