sched/fair: Add comments to explain select_idle_sibling()

[cascardo/linux.git] / kernel / tsacct.c

diff --git a/kernel/tsacct.c b/kernel/tsacct.c
index 975cb49..f8e26ab 100644 (file)
--- a/kernel/tsacct.c
+++ b/kernel/tsacct.c
@@ -93,9 +93,11 @@ void xacct_add_tsk(struct taskstats *stats, struct task_struct *p)
 {
        struct mm_struct *mm;
 
-       /* convert pages-usec to Mbyte-usec */
-       stats->coremem = p->acct_rss_mem1 * PAGE_SIZE / MB;
-       stats->virtmem = p->acct_vm_mem1 * PAGE_SIZE / MB;
+       /* convert pages-nsec/1024 to Mbyte-usec, see __acct_update_integrals */
+       stats->coremem = p->acct_rss_mem1 * PAGE_SIZE;
+       do_div(stats->coremem, 1000 * KB);
+       stats->virtmem = p->acct_vm_mem1 * PAGE_SIZE;
+       do_div(stats->virtmem, 1000 * KB);
        mm = get_task_mm(p);
        if (mm) {
                /* adjust to KB unit */
@@ -123,27 +125,28 @@ void xacct_add_tsk(struct taskstats *stats, struct task_struct *p)
 static void __acct_update_integrals(struct task_struct *tsk,
                                    cputime_t utime, cputime_t stime)
 {
-       if (likely(tsk->mm)) {
-               cputime_t time, dtime;
-               struct timeval value;
-               unsigned long flags;
-               u64 delta;
-
-               local_irq_save(flags);
-               time = stime + utime;
-               dtime = time - tsk->acct_timexpd;
-               jiffies_to_timeval(cputime_to_jiffies(dtime), &value);
-               delta = value.tv_sec;
-               delta = delta * USEC_PER_SEC + value.tv_usec;
-
-               if (delta == 0)
-                       goto out;
-               tsk->acct_timexpd = time;
-               tsk->acct_rss_mem1 += delta * get_mm_rss(tsk->mm);
-               tsk->acct_vm_mem1 += delta * tsk->mm->total_vm;
-       out:
-               local_irq_restore(flags);
-       }
+       cputime_t time, dtime;
+       u64 delta;
+
+       if (!likely(tsk->mm))
+               return;
+
+       time = stime + utime;
+       dtime = time - tsk->acct_timexpd;
+       /* Avoid division: cputime_t is often in nanoseconds already. */
+       delta = cputime_to_nsecs(dtime);
+
+       if (delta < TICK_NSEC)
+               return;
+
+       tsk->acct_timexpd = time;
+       /*
+        * Divide by 1024 to avoid overflow, and to avoid division.
+        * The final unit reported to userspace is Mbyte-usecs,
+        * the rest of the math is done in xacct_add_tsk.
+        */
+       tsk->acct_rss_mem1 += delta * get_mm_rss(tsk->mm) >> 10;
+       tsk->acct_vm_mem1 += delta * tsk->mm->total_vm >> 10;
 }
 
 /**
@@ -153,9 +156,12 @@ static void __acct_update_integrals(struct task_struct *tsk,
 void acct_update_integrals(struct task_struct *tsk)
 {
        cputime_t utime, stime;
+       unsigned long flags;
 
+       local_irq_save(flags);
        task_cputime(tsk, &utime, &stime);
        __acct_update_integrals(tsk, utime, stime);
+       local_irq_restore(flags);
 }
 
 /**