[RFC PATCH v1 2/3] Make calls to account_scaled_stats

[Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>]

Hook various accounting functions to call scaled stats

* Hook porcess contect switch: __switch_to()
* Hook IRQ handling account_system_vtime() in hardirq.hA
* Update __delayacct_add_tsk() to take care of scaling by 1000
* Update bacct_add_tsk() to take care of scaling by 1000

Signed-off-by: Amit K. Arora <aarora@linux.vnet.ibm.com>
Signed-off-by: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
---

 arch/x86/kernel/process_32.c |    8 ++++++++
 include/linux/hardirq.h      |    4 ++++
 kernel/delayacct.c           |    7 ++++++-
 kernel/timer.c               |    2 --
 kernel/tsacct.c              |   10 ++++++++--
 5 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index f8476df..c81a783 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -56,6 +56,9 @@
 #include <asm/cpu.h>
 #include <asm/kdebug.h>
 
+extern void account_scaled_stats(struct task_struct *tsk);
+extern void reset_for_scaled_stats(struct task_struct *tsk);
+
 asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
 
 static int hlt_counter;
@@ -660,6 +663,11 @@ struct task_struct * __switch_to(struct task_struct *prev_p, struct task_struct
 		loadsegment(gs, next->gs);
 
 	x86_write_percpu(current_task, next_p);
+	/* Account scaled statistics for the task leaving CPU */
+	account_scaled_stats(prev_p);
+	barrier();
+	/* Initialise stats counter for new task */
+	reset_for_scaled_stats(next_p);
 
 	return prev_p;
 }
diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h
index 181006c..4458736 100644
--- a/include/linux/hardirq.h
+++ b/include/linux/hardirq.h
@@ -7,6 +7,9 @@
 #include <asm/hardirq.h>
 #include <asm/system.h>
 
+/* TBD: Add config option */
+extern void account_scaled_stats(struct task_struct *tsk);
+
 /*
  * We put the hardirq and softirq counter into the preemption
  * counter. The bitmask has the following meaning:
@@ -115,6 +118,7 @@ struct task_struct;
 #ifndef CONFIG_VIRT_CPU_ACCOUNTING
 static inline void account_system_vtime(struct task_struct *tsk)
 {
+	account_scaled_stats(tsk);
 }
 #endif
 
diff --git a/kernel/delayacct.c b/kernel/delayacct.c
index 10e43fd..3e2938f 100644
--- a/kernel/delayacct.c
+++ b/kernel/delayacct.c
@@ -117,7 +117,12 @@ int __delayacct_add_tsk(struct taskstats *d, struct task_struct *tsk)
 
 	tmp = (s64)d->cpu_scaled_run_real_total;
 	cputime_to_timespec(tsk->utimescaled + tsk->stimescaled, &ts);
-	tmp += timespec_to_ns(&ts);
+	/* HACK: Remember, we multipled the cputime_t by 1000 to include
+	 * fraction.  Now it is time to scale it back to correct 'ns' value.
+	 * Perhaps, we should use nano second unit (u64 type) for utimescaled 
+	 * and stimescaled?
+	 */
+	tmp += div_s64(timespec_to_ns(&ts),1000);
 	d->cpu_scaled_run_real_total =
 		(tmp < (s64)d->cpu_scaled_run_real_total) ? 0 : tmp;
 
diff --git a/kernel/timer.c b/kernel/timer.c
index ceacc66..de8a615 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -964,10 +964,8 @@ void account_process_tick(struct task_struct *p, int user_tick)
 
 	if (user_tick) {
 		account_user_time(p, one_jiffy);
-		account_user_time_scaled(p, cputime_to_scaled(one_jiffy));
 	} else {
 		account_system_time(p, HARDIRQ_OFFSET, one_jiffy);
-		account_system_time_scaled(p, cputime_to_scaled(one_jiffy));
 	}
 }
 #endif
diff --git a/kernel/tsacct.c b/kernel/tsacct.c
index 4ab1b58..ee0d93b 100644
--- a/kernel/tsacct.c
+++ b/kernel/tsacct.c
@@ -62,10 +62,16 @@ void bacct_add_tsk(struct taskstats *stats, struct task_struct *tsk)
 	rcu_read_unlock();
 	stats->ac_utime	 = cputime_to_msecs(tsk->utime) * USEC_PER_MSEC;
 	stats->ac_stime	 = cputime_to_msecs(tsk->stime) * USEC_PER_MSEC;
+	/* HACK: cputime unit is jiffies on x86 and not good for fractional 
+	 * additional.  cputime_t type {u,s}timescaled is multiplied by 
+	 * 1000 for scaled accounting.  Hence, cputime_to_msecs will actually 
+	 * give the required micro second value.  The multiplier 
+	 * USEC_PER_MSEC has been dropped.
+	 */
 	stats->ac_utimescaled =
-		cputime_to_msecs(tsk->utimescaled) * USEC_PER_MSEC;
+		cputime_to_msecs(tsk->utimescaled);
 	stats->ac_stimescaled =
-		cputime_to_msecs(tsk->stimescaled) * USEC_PER_MSEC;
+		cputime_to_msecs(tsk->stimescaled);
 	stats->ac_minflt = tsk->min_flt;
 	stats->ac_majflt = tsk->maj_flt;