[PATCH] per-task-delay-accounting: /proc export of aggregated block I/O delays

Export I/O delays seen by a task through /proc/<tgid>/stats for use in top
etc.

Note that delays for I/O done for swapping in pages (swapin I/O) is clubbed
together with all other I/O here (this is not the case in the netlink
interface where the swapin I/O is kept distinct)

[akpm@osdl.org: printk warning fix]
Signed-off-by: Shailabh Nagar <nagar@watson.ibm.com>
Signed-off-by: Balbir Singh <balbir@in.ibm.com>
Cc: Jes Sorensen <jes@sgi.com>
Cc: Peter Chubb <peterc@gelato.unsw.edu.au>
Cc: Erich Focht <efocht@ess.nec.de>
Cc: Levent Serinol <lserinol@gmail.com>
Cc: Jay Lan <jlan@engr.sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/proc/array.c

@@ -74,6 +74,7 @@
 #include <linux/times.h>
 #include <linux/cpuset.h>
 #include <linux/rcupdate.h>
+#include <linux/delayacct.h>
 
 #include <asm/uaccess.h>
 #include <asm/pgtable.h>
@@ -411,7 +412,7 @@ static int do_task_stat(struct task_struct *task, char * buffer, int whole)
 
 	res = sprintf(buffer,"%d (%s) %c %d %d %d %d %d %lu %lu \
 %lu %lu %lu %lu %lu %ld %ld %ld %ld %d 0 %llu %lu %ld %lu %lu %lu %lu %lu \
-%lu %lu %lu %lu %lu %lu %lu %lu %d %d %lu %lu\n",
+%lu %lu %lu %lu %lu %lu %lu %lu %d %d %lu %lu %llu\n",
 		task->pid,
 		tcomm,
 		state,
@@ -455,7 +456,8 @@ static int do_task_stat(struct task_struct *task, char * buffer, int whole)
 		task->exit_signal,
 		task_cpu(task),
 		task->rt_priority,
-		task->policy);
+		task->policy,
+		(unsigned long long)delayacct_blkio_ticks(task));
 	if(mm)
 		mmput(mm);
 	return res;

include/linux/delayacct.h

@@ -37,6 +37,7 @@ extern void __delayacct_tsk_exit(struct task_struct *);
 extern void __delayacct_blkio_start(void);
 extern void __delayacct_blkio_end(void);
 extern int __delayacct_add_tsk(struct taskstats *, struct task_struct *);
+extern __u64 __delayacct_blkio_ticks(struct task_struct *);
 
 static inline void delayacct_set_flag(int flag)
 {
@@ -86,6 +87,13 @@ static inline int delayacct_add_tsk(struct taskstats *d,
 	return __delayacct_add_tsk(d, tsk);
 }
 
+static inline __u64 delayacct_blkio_ticks(struct task_struct *tsk)
+{
+	if (tsk->delays)
+		return __delayacct_blkio_ticks(tsk);
+	return 0;
+}
+
 #else
 static inline void delayacct_set_flag(int flag)
 {}
@@ -104,6 +112,8 @@ static inline void delayacct_blkio_end(void)
 static inline int delayacct_add_tsk(struct taskstats *d,
 					struct task_struct *tsk)
 { return 0; }
+static inline __u64 delayacct_blkio_ticks(struct task_struct *tsk)
+{ return 0; }
 #endif /* CONFIG_TASK_DELAY_ACCT */
 
 #endif

kernel/delayacct.c

@@ -164,3 +164,15 @@ int __delayacct_add_tsk(struct taskstats *d, struct task_struct *tsk)
 	spin_unlock(&tsk->delays_lock);
 	return 0;
 }
+
+__u64 __delayacct_blkio_ticks(struct task_struct *tsk)
+{
+	__u64 ret;
+
+	spin_lock(&tsk->delays->lock);
+	ret = nsec_to_clock_t(tsk->delays->blkio_delay +
+				tsk->delays->swapin_delay);
+	spin_unlock(&tsk->delays->lock);
+	return ret;
+}
+