[PATCH v2 2/2] delayacct: add a proc file to dump the delay info

[brookxu]

From: Chunguang Xu <brookxu@xxxxxxxxxxx>

Many distributions do not install the getdelay tool by
default, similar to task_io_accounting, adding a proc
file to make access easier.

v2: Fix some errors prompted by the kernel test robot.

Signed-off-by: Chunguang Xu <brookxu@xxxxxxxxxxx>
Reported-by: kernel test robot <lkp@xxxxxxxxx>
---
 fs/proc/base.c     |  7 +++++++
 kernel/delayacct.c | 41 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index b3422cd..4de261a 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -96,6 +96,7 @@
 #include <linux/posix-timers.h>
 #include <linux/time_namespace.h>
 #include <linux/resctrl.h>
+#include <linux/delayacct.h>
 #include <trace/events/oom.h>
 #include "internal.h"
 #include "fd.h"
@@ -3244,6 +3245,9 @@ static int proc_stack_depth(struct seq_file *m, struct pid_namespace *ns,
 #ifdef CONFIG_TASK_IO_ACCOUNTING
 	ONE("io",	S_IRUSR, proc_tgid_io_accounting),
 #endif
+#ifdef CONFIG_TASK_DELAY_ACCT
+	ONE("delays",	S_IRUSR, proc_delayacct_show),
+#endif
 #ifdef CONFIG_USER_NS
 	REG("uid_map",    S_IRUGO|S_IWUSR, proc_uid_map_operations),
 	REG("gid_map",    S_IRUGO|S_IWUSR, proc_gid_map_operations),
@@ -3583,6 +3587,9 @@ static int proc_tid_comm_permission(struct inode *inode, int mask)
 #ifdef CONFIG_TASK_IO_ACCOUNTING
 	ONE("io",	S_IRUSR, proc_tid_io_accounting),
 #endif
+#ifdef CONFIG_TASK_DELAY_ACCT
+	ONE("delays",	S_IRUSR, proc_delayacct_show),
+#endif
 #ifdef CONFIG_USER_NS
 	REG("uid_map",    S_IRUGO|S_IWUSR, proc_uid_map_operations),
 	REG("gid_map",    S_IRUGO|S_IWUSR, proc_gid_map_operations),
diff --git a/kernel/delayacct.c b/kernel/delayacct.c
index ec580cb..87d091a 100644
--- a/kernel/delayacct.c
+++ b/kernel/delayacct.c
@@ -14,6 +14,7 @@
 #include <linux/sysctl.h>
 #include <linux/delayacct.h>
 #include <linux/module.h>
+#include <linux/seq_file.h>
 
 int delayacct_on __read_mostly = 1;	/* Delay accounting turned on/off */
 EXPORT_SYMBOL_GPL(delayacct_on);
@@ -26,6 +27,18 @@ static int __init delayacct_setup_disable(char *str)
 }
 __setup("nodelayacct", delayacct_setup_disable);
 
+struct delayacct_stat {
+	const char *name;
+	unsigned int idx;
+};
+
+static struct delayacct_stat delayacct_stats[] = {
+	{"blkio", DELAYACCT_BLKIO},
+	{"swapin", DELAYACCT_SWAPIN},
+	{"pagecache_thrashing", DELAYACCT_THRASHING},
+	{"mem_reclaim", DELAYACCT_FREEPAGES}
+};
+
 void delayacct_init(void)
 {
 	delayacct_cache = KMEM_CACHE(task_delay_info, SLAB_PANIC|SLAB_ACCOUNT);
@@ -126,3 +139,31 @@ u64 __delayacct_blkio_ticks(struct task_struct *tsk)
 	return ret;
 }
 
+#define K(x) ({ u64 _tmp = x; do_div(_tmp, 1000); _tmp; })
+
+int proc_delayacct_show(struct seq_file *m, struct pid_namespace *ns,
+		       struct pid *pid, struct task_struct *task)
+{
+	struct delayacct_count *delays;
+	int idx;
+
+	if (!task->delays)
+		return 0;
+
+	delays = task->delays->delays;
+	for (idx = 0; idx < ARRAY_SIZE(delayacct_stats); idx++) {
+		u32 item = delayacct_stats[idx].idx;
+		u64 mean = delays[item].delay;
+
+		if (delays[item].count)
+			do_div(mean, delays[item].count);
+
+		seq_printf(m, "%s %llu %llu %u %llu\n",
+			   delayacct_stats[idx].name,
+			   K(mean),
+			   K(delays[item].max),
+			   delays[item].count,
+			   K(delays[item].delay));
+	}
+	return 0;
+}
-- 
1.8.3.1