On Fri, 2008-05-02 at 21:27 +0200, Mike Galbraith wrote:
That's a quite horrible patch for some of us, but I think I know why you
did that, and I think your fancy Q6600 has a stable enough TSC to pull
it off.
Let me try and come up with something slightly less horrible
Ok, the the below would need something that relates tick_timestamp's to
one another.. probably sucks without it..
OTOH, Andi said he was working on a fastish global sched_clock() thingy,
Andi got a link to that code?
Index: linux-2.6-2/kernel/sched.c
===================================================================
--- linux-2.6-2.orig/kernel/sched.c
+++ linux-2.6-2/kernel/sched.c
@@ -560,6 +560,7 @@ struct rq {
unsigned long next_balance;
struct mm_struct *prev_mm;
+ spinlock_t clock_lock;
u64 clock, prev_clock_raw;
s64 clock_max_delta;
@@ -657,20 +658,25 @@ static inline void update_last_tick_seen
}
#endif
+#define cpu_rq(cpu) (&per_cpu(runqueues, (cpu)))
+#define this_rq() (&__get_cpu_var(runqueues))
+#define task_rq(p) cpu_rq(task_cpu(p))
+#define cpu_curr(cpu) (cpu_rq(cpu)->curr)
+
/*
* Update the per-runqueue clock, as finegrained as the platform can give
* us, but without assuming monotonicity, etc.:
*/
-static void __update_rq_clock(struct rq *rq)
+static void ___update_rq_clock(struct rq *rq, u64 now)
{
u64 prev_raw = rq->prev_clock_raw;
- u64 now = sched_clock();
s64 delta = now - prev_raw;
u64 clock = rq->clock;
#ifdef CONFIG_SCHED_DEBUG
WARN_ON_ONCE(cpu_of(rq) != smp_processor_id());
#endif
+ spin_lock(&rq->clock_lock);
/*
* Protect against sched_clock() occasionally going backwards:
*/
@@ -699,12 +705,31 @@ static void __update_rq_clock(struct rq
rq->prev_clock_raw = now;
rq->clock = clock;
+ spin_unlock(&rq->clock_lock);
+}
+
+static void __update_rq_clock(struct rq *rq)
+{
+ ___update_rq_clock(rq, sched_clock());
+}
+
+static void __update_remote_rq_clock(struct rq *rq)
+{
+ u64 now = sched_clock();
+ struct rq *this_rq = this_rq();
+
+ now -= this_rq->tick_timestamp;
+ now += rq->tick_timestamp;
+
+ ___update_rq_clock(rq, now);
}
static void update_rq_clock(struct rq *rq)
{
if (likely(smp_processor_id() == cpu_of(rq)))
__update_rq_clock(rq);
+ else
+ __update_remote_rq_clock(rq);
}
/*
@@ -717,11 +742,6 @@ static void update_rq_clock(struct rq *r
#define for_each_domain(cpu, __sd) \
for (__sd = rcu_dereference(cpu_rq(cpu)->sd); __sd; __sd = __sd->parent)
-#define cpu_rq(cpu) (&per_cpu(runqueues, (cpu)))
-#define this_rq() (&__get_cpu_var(runqueues))
-#define task_rq(p) cpu_rq(task_cpu(p))
-#define cpu_curr(cpu) (cpu_rq(cpu)->curr)
-
/*
* Tunables that become constants when CONFIG_SCHED_DEBUG is off:
*/
@@ -8147,6 +8167,7 @@ void __init sched_init(void)
rq = cpu_rq(i);
spin_lock_init(&rq->lock);
+ spin_lock_init(&rq->clock_lock);
lockdep_set_class(&rq->lock, &rq->rq_lock_key);
rq->nr_running = 0;
rq->clock = 1;
--
