[PATCH 2/3] delayacct: Add a proc file to dump the delay info

[brookxu]

From: Chunguang Xu <broo...@tencent.com>

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

Signed-off-by: Chunguang Xu <broo...@tencent.com>
---
 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..990af3b 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;
+};
+
+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) ((x) / 1000)
+
+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 = 0;
+
+               if (delays[item].count)
+                       mean = div_u64(delays[item].delay, delays[item].count);
+
+               seq_printf(m, "%s %llu %llu %llu %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