[PATCH] per-task-delay-accounting: delay accounting usage of taskstats interface

Usage of taskstats interface by delay accounting.

Signed-off-by: Shailabh Nagar <nagar@us.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>

7 files changed, 144 insertions, 7 deletions

diff --git a/include/linux/delayacct.h b/include/linux/delayacct.h
index 0ecbf9aad8e1..d955078a1441 100644
--- a/include/linux/delayacct.h
+++ b/include/linux/delayacct.h
@@ -18,6 +18,7 @@
 #define _LINUX_DELAYACCT_H
 
 #include <linux/sched.h>
+#include <linux/taskstats_kern.h>
 
 /*
  * Per-task flags relevant to delay accounting
@@ -35,6 +36,7 @@ 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);
+extern int __delayacct_add_tsk(struct taskstats *, struct task_struct *);
 
 static inline void delayacct_set_flag(int flag)
 {
@@ -74,6 +76,16 @@ static inline void delayacct_blkio_end(void)
                 __delayacct_blkio_end();
 }
 
+static inline int delayacct_add_tsk(struct taskstats *d,
+                                        struct task_struct *tsk)
+{
+        if (likely(!delayacct_on))
+                return -EINVAL;
+        if (!tsk->delays)
+                return 0;
+        return __delayacct_add_tsk(d, tsk);
+}
+
 #else
 static inline void delayacct_set_flag(int flag)
 {}
@@ -89,6 +101,9 @@ static inline void delayacct_blkio_start(void)
 {}
 static inline void delayacct_blkio_end(void)
 {}
+static inline int delayacct_add_tsk(struct taskstats *d,
+                                        struct task_struct *tsk)
+{ return 0; }
 #endif /* CONFIG_TASK_DELAY_ACCT */
 
 #endif
diff --git a/include/linux/sched.h b/include/linux/sched.h
index f751062d89a2..3c5610ca0c92 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -990,6 +990,7 @@ struct task_struct {
          */
         struct pipe_inode_info *splice_pipe;
 #ifdef  CONFIG_TASK_DELAY_ACCT
+        spinlock_t delays_lock;
         struct task_delay_info *delays;
 #endif
 };
diff --git a/include/linux/taskstats.h b/include/linux/taskstats.h
index 51f62759bea9..c6aeca32348e 100644
--- a/include/linux/taskstats.h
+++ b/include/linux/taskstats.h
@@ -34,7 +34,60 @@
 struct taskstats {
 
         /* Version 1 */
-        __u64   version;
+        __u16   version;
+        __u16   padding[3];     /* Userspace should not interpret the padding
+                                 * field which can be replaced by useful
+                                 * fields if struct taskstats is extended.
+                                 */
+
+        /* Delay accounting fields start
+         *
+         * All values, until comment "Delay accounting fields end" are
+         * available only if delay accounting is enabled, even though the last
+         * few fields are not delays
+         *
+         * xxx_count is the number of delay values recorded
+         * xxx_delay_total is the corresponding cumulative delay in nanoseconds
+         *
+         * xxx_delay_total wraps around to zero on overflow
+         * xxx_count incremented regardless of overflow
+         */
+
+        /* Delay waiting for cpu, while runnable
+         * count, delay_total NOT updated atomically
+         */
+        __u64   cpu_count;
+        __u64   cpu_delay_total;
+
+        /* Following four fields atomically updated using task->delays->lock */
+
+        /* Delay waiting for synchronous block I/O to complete
+         * does not account for delays in I/O submission
+         */
+        __u64   blkio_count;
+        __u64   blkio_delay_total;
+
+        /* Delay waiting for page fault I/O (swap in only) */
+        __u64   swapin_count;
+        __u64   swapin_delay_total;
+
+        /* cpu "wall-clock" running time
+         * On some architectures, value will adjust for cpu time stolen
+         * from the kernel in involuntary waits due to virtualization.
+         * Value is cumulative, in nanoseconds, without a corresponding count
+         * and wraps around to zero silently on overflow
+         */
+        __u64   cpu_run_real_total;
+
+        /* cpu "virtual" running time
+         * Uses time intervals seen by the kernel i.e. no adjustment
+         * for kernel's involuntary waits due to virtualization.
+         * Value is cumulative, in nanoseconds, without a corresponding count
+         * and wraps around to zero silently on overflow
+         */
+        __u64   cpu_run_virtual_total;
+        /* Delay accounting fields end */
+        /* version 1 ends here */
 };
 
 
diff --git a/include/linux/taskstats_kern.h b/include/linux/taskstats_kern.h
index bd0ecb969c26..fc9da2e26443 100644
--- a/include/linux/taskstats_kern.h
+++ b/include/linux/taskstats_kern.h
@@ -17,6 +17,7 @@ enum {
 
 #ifdef CONFIG_TASKSTATS
 extern kmem_cache_t *taskstats_cache;
+extern struct mutex taskstats_exit_mutex;
 
 static inline void taskstats_exit_alloc(struct taskstats **ptidstats,
                                         struct taskstats **ptgidstats)
diff --git a/init/Kconfig b/init/Kconfig
index 56a7093b4e4c..a099fc6526d9 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -173,6 +173,7 @@ config TASKSTATS
 
 config TASK_DELAY_ACCT
         bool "Enable per-task delay accounting (EXPERIMENTAL)"
+        depends on TASKSTATS
         help
           Collect information on time spent by a task waiting for system
           resources like cpu, synchronous block I/O completion and swapping
diff --git a/kernel/delayacct.c b/kernel/delayacct.c
index 3546b0800f9f..1be274a462ca 100644
--- a/kernel/delayacct.c
+++ b/kernel/delayacct.c
@@ -41,6 +41,10 @@ void delayacct_init(void)
 
 void __delayacct_tsk_init(struct task_struct *tsk)
 {
+        spin_lock_init(&tsk->delays_lock);
+        /* No need to acquire tsk->delays_lock for allocation here unless
+           __delayacct_tsk_init called after tsk is attached to tasklist
+        */
         tsk->delays = kmem_cache_zalloc(delayacct_cache, SLAB_KERNEL);
         if (tsk->delays)
                 spin_lock_init(&tsk->delays->lock);
@@ -48,8 +52,11 @@ void __delayacct_tsk_init(struct task_struct *tsk)
 
 void __delayacct_tsk_exit(struct task_struct *tsk)
 {
-        kmem_cache_free(delayacct_cache, tsk->delays);
+        struct task_delay_info *delays = tsk->delays;
+        spin_lock(&tsk->delays_lock);
         tsk->delays = NULL;
+        spin_unlock(&tsk->delays_lock);
+        kmem_cache_free(delayacct_cache, delays);
 }
 
 /*
@@ -104,3 +111,56 @@ void __delayacct_blkio_end(void)
                         &current->delays->blkio_delay,
                         &current->delays->blkio_count);
 }
+
+int __delayacct_add_tsk(struct taskstats *d, struct task_struct *tsk)
+{
+        s64 tmp;
+        struct timespec ts;
+        unsigned long t1,t2,t3;
+
+        spin_lock(&tsk->delays_lock);
+
+        /* Though tsk->delays accessed later, early exit avoids
+         * unnecessary returning of other data
+         */
+        if (!tsk->delays)
+                goto done;
+
+        tmp = (s64)d->cpu_run_real_total;
+        cputime_to_timespec(tsk->utime + tsk->stime, &ts);
+        tmp += timespec_to_ns(&ts);
+        d->cpu_run_real_total = (tmp < (s64)d->cpu_run_real_total) ? 0 : tmp;
+
+        /*
+         * No locking available for sched_info (and too expensive to add one)
+         * Mitigate by taking snapshot of values
+         */
+        t1 = tsk->sched_info.pcnt;
+        t2 = tsk->sched_info.run_delay;
+        t3 = tsk->sched_info.cpu_time;
+
+        d->cpu_count += t1;
+
+        jiffies_to_timespec(t2, &ts);
+        tmp = (s64)d->cpu_delay_total + timespec_to_ns(&ts);
+        d->cpu_delay_total = (tmp < (s64)d->cpu_delay_total) ? 0 : tmp;
+
+        tmp = (s64)d->cpu_run_virtual_total + (s64)jiffies_to_usecs(t3) * 1000;
+        d->cpu_run_virtual_total =
+                (tmp < (s64)d->cpu_run_virtual_total) ? 0 : tmp;
+
+        /* zero XXX_total, non-zero XXX_count implies XXX stat overflowed */
+
+        spin_lock(&tsk->delays->lock);
+        tmp = d->blkio_delay_total + tsk->delays->blkio_delay;
+        d->blkio_delay_total = (tmp < d->blkio_delay_total) ? 0 : tmp;
+        tmp = d->swapin_delay_total + tsk->delays->swapin_delay;
+        d->swapin_delay_total = (tmp < d->swapin_delay_total) ? 0 : tmp;
+        d->blkio_count += tsk->delays->blkio_count;
+        d->swapin_count += tsk->delays->swapin_count;
+        spin_unlock(&tsk->delays->lock);
+
+done:
+        spin_unlock(&tsk->delays_lock);
+        return 0;
+}
diff --git a/kernel/taskstats.c b/kernel/taskstats.c
index 82ec9137d908..ea9506de3b85 100644
--- a/kernel/taskstats.c
+++ b/kernel/taskstats.c
@@ -18,13 +18,13 @@
 
 #include <linux/kernel.h>
 #include <linux/taskstats_kern.h>
+#include <linux/delayacct.h>
 #include <net/genetlink.h>
 #include <asm/atomic.h>
 
 static DEFINE_PER_CPU(__u32, taskstats_seqnum) = { 0 };
 static int family_registered;
 kmem_cache_t *taskstats_cache;
-static DEFINE_MUTEX(taskstats_exit_mutex);
 
 static struct genl_family family = {
         .id             = GENL_ID_GENERATE,
@@ -120,7 +120,10 @@ static int fill_pid(pid_t pid, struct task_struct *pidtsk,
          *              goto err;
          */
 
-err:
+        rc = delayacct_add_tsk(stats, tsk);
+        stats->version = TASKSTATS_VERSION;
+
+        /* Define err: label here if needed */
         put_task_struct(tsk);
         return rc;
 
@@ -152,8 +155,14 @@ static int fill_tgid(pid_t tgid, struct task_struct *tgidtsk,
                  *              break;
                  */
 
+                rc = delayacct_add_tsk(stats, tsk);
+                if (rc)
+                        break;
+
         } while_each_thread(first, tsk);
         read_unlock(&tasklist_lock);
+        stats->version = TASKSTATS_VERSION;
+
 
         /*
          * Accounting subsytems can also add calls here if they don't
@@ -233,8 +242,6 @@ void taskstats_exit_send(struct task_struct *tsk, struct taskstats *tidstats,
         if (!family_registered || !tidstats)
                 return;
 
-        mutex_lock(&taskstats_exit_mutex);
-
         is_thread_group = !thread_group_empty(tsk);
         rc = 0;
 
@@ -292,7 +299,6 @@ nla_put_failure:
 err_skb:
         nlmsg_free(rep_skb);
 ret:
-        mutex_unlock(&taskstats_exit_mutex);
         return;
 }