Hi Volodymyr,
On 12/06/2020 12:44, Volodymyr Babchuk wrote:
On Fri, 2020-06-12 at 06:57 +0200, Jürgen Groß wrote:
On 12.06.20 02:22, Volodymyr Babchuk wrote:
As scheduler code now collects time spent in IRQ handlers and in
do_softirq(), we can present those values to userspace tools like
xentop, so system administrator can see how system behaves.
We are updating counters only in sched_get_time_correction() function
to minimize number of taken spinlocks. As atomic_t is 32 bit wide, it
is not enough to store time with nanosecond precision. So we need to
use 64 bit variables and protect them with spinlock.
Signed-off-by: Volodymyr Babchuk <volodymyr_babc...@epam.com>
---
xen/common/sched/core.c | 17 +++++++++++++++++
xen/common/sysctl.c | 1 +
xen/include/public/sysctl.h | 4 +++-
xen/include/xen/sched.h | 2 ++
4 files changed, 23 insertions(+), 1 deletion(-)
diff --git a/xen/common/sched/core.c b/xen/common/sched/core.c
index a7294ff5c3..ee6b1d9161 100644
--- a/xen/common/sched/core.c
+++ b/xen/common/sched/core.c
@@ -95,6 +95,10 @@ static struct scheduler __read_mostly ops;
static bool scheduler_active;
+static DEFINE_SPINLOCK(sched_stat_lock);
+s_time_t sched_stat_irq_time;
+s_time_t sched_stat_hyp_time;
+
static void sched_set_affinity(
struct sched_unit *unit, const cpumask_t *hard, const cpumask_t *soft);
@@ -994,9 +998,22 @@ s_time_t sched_get_time_correction(struct sched_unit *u)
break;
}
+ spin_lock_irqsave(&sched_stat_lock, flags);
+ sched_stat_irq_time += irq;
+ sched_stat_hyp_time += hyp;
+ spin_unlock_irqrestore(&sched_stat_lock, flags);
Please don't use a lock. Just use add_sized() instead which will add
atomically.
Looks like arm does not support 64 bit variables. >
Julien, I believe, this is armv7 limitation? Should armv8 work with 64-
bit atomics?
64-bit atomics can work on both Armv7 and Armv8 :). It just haven't been
plumbed yet.
I am happy to write a patch if you need atomic64_t or even a 64-bit
add_sized().
Cheers,
--
Julien Grall
