[PATCH] per-task-delay-accounting: sync block I/O and swapin delay collection

Unlike earlier iterations of the delay accounting patches, now delays are only
collected for the actual I/O waits rather than try and cover the delays seen
in I/O submission paths.

Account separately for block I/O delays incurred as a result of swapin page
faults whose frequency can be affected by the task/process' rss limit.  Hence
swapin delays can act as feedback for rss limit changes independent of I/O
priority changes.

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>

1 files changed, 25 insertions, 0 deletions

diff --git a/include/linux/delayacct.h b/include/linux/delayacct.h
index 9572cfa1f129..0ecbf9aad8e1 100644
--- a/include/linux/delayacct.h
+++ b/include/linux/delayacct.h
@@ -19,6 +19,13 @@
 
 #include <linux/sched.h>
 
+/*
+ * Per-task flags relevant to delay accounting
+ * maintained privately to avoid exhausting similar flags in sched.h:PF_*
+ * Used to set current->delays->flags
+ */
+#define DELAYACCT_PF_SWAPIN     0x00000001      /* I am doing a swapin */
+
 #ifdef CONFIG_TASK_DELAY_ACCT
 
 extern int delayacct_on;        /* Delay accounting turned on/off */
@@ -26,6 +33,8 @@ extern kmem_cache_t *delayacct_cache;
 extern void delayacct_init(void);
 extern void __delayacct_tsk_init(struct task_struct *);
 extern void __delayacct_tsk_exit(struct task_struct *);
+extern void __delayacct_blkio_start(void);
+extern void __delayacct_blkio_end(void);
 
 static inline void delayacct_set_flag(int flag)
 {
@@ -53,6 +62,18 @@ static inline void delayacct_tsk_exit(struct task_struct *tsk)
                 __delayacct_tsk_exit(tsk);
 }
 
+static inline void delayacct_blkio_start(void)
+{
+        if (current->delays)
+                __delayacct_blkio_start();
+}
+
+static inline void delayacct_blkio_end(void)
+{
+        if (current->delays)
+                __delayacct_blkio_end();
+}
+
 #else
 static inline void delayacct_set_flag(int flag)
 {}
@@ -64,6 +85,10 @@ static inline void delayacct_tsk_init(struct task_struct *tsk)
 {}
 static inline void delayacct_tsk_exit(struct task_struct *tsk)
 {}
+static inline void delayacct_blkio_start(void)
+{}
+static inline void delayacct_blkio_end(void)
+{}
 #endif /* CONFIG_TASK_DELAY_ACCT */
 
 #endif