Andrew Morton wrote:
Jack Steiner <[email protected]> wrote:
+unsigned long nr_active(void)
+{
+ unsigned long i, running = 0, uninterruptible = 0;
+
+ for_each_online_cpu(i) {
+ running += cpu_rq(i)->nr_running;
+ uninterruptible += cpu_rq(i)->nr_uninterruptible;
+ }
+
+ if (unlikely((long)uninterruptible < 0))
+ uninterruptible = 0;
+
+ return running + uninterruptible;
+}
Is that check for (uninterruptible < 0) (copied from nr_uninterruptible)
really needed? Can rq->nr_uninterruptible actually go negative?
The sum cannot if there are no concurrent updates, however when
there are concurrent updates then it can go negative.
rq->nr_uninterruptible itself is meaningless because it can be
incremented on one rq and decremented on another.
Perhaps nr_context_switches() and nr_iowait() should also go into this
function, then we rename it all to
struct sched_stuff {
unsigned nr_uninterruptible;
unsigned nr_running;
unsigned nr_active;
unsigned long nr_context_switches;
};
void get_sched_stuff(struct sched_stuff *);
and then convert all those random little counter-upper-callers we have.
Is there a need? Do they (except calc_load) use multiple values at
the same time?
And then give get_sched_stuff() a hotplug handler (probably unneeded) and
What would the hotplug handler do?
then scratch our heads over why nr_uninterruptible() iterates across all
possible CPUs while this new nr_active() iterates over all online CPUs like
nr_running() and unlike nr_context_switches().
I think it need only iterate over possible CPUs.
IOW: this code's an inefficient mess and needs some caring for.
What are the performance critical places that call the nr_blah() functions?
--
SUSE Labs, Novell Inc.
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