Re: [Xen-devel] [PATCH 2 of 3] xen: tracing: introduce per-scheduler trace event IDs

[George Dunlap <George.Dunlap@xxxxxxxxxxxxx>]

On Mon, Dec 3, 2012 at 4:34 PM, Dario Faggioli <raistlin@xxxxxxxx> wrote:

So that it becomes possible to create specific scheduling event
within each scheduler without worrying about the overlapping,
and also without giving up being able to recognise them
univocally. The latter is deemed as useful, since we can have
more than one scheduler running at the same time, thanks to
cpupools.

The event ID is 12 bits, and this change uses the upper 3 of them
for the 'scheduler ID'. This means we're limited to 8 schedulers
and to 512 scheduler specific tracing events. Both seem reasonable
limitations as of now.

This also converts the existing credit2 tracing (the only scheduler
generating tracing events up to now) to the new system.

Signed-off-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx>

 

diff --git a/xen/common/sched_credit2.c b/xen/common/sched_credit2.c
--- a/xen/common/sched_credit2.c
+++ b/xen/common/sched_credit2.c
@@ -29,18 +29,24 @@
 #define d2printk(x...)
 //#define d2printk printk

-#define TRC_CSCHED2_TICK        TRC_SCHED_CLASS + 1
-#define TRC_CSCHED2_RUNQ_POS    TRC_SCHED_CLASS + 2
-#define TRC_CSCHED2_CREDIT_BURN TRC_SCHED_CLASS + 3
-#define TRC_CSCHED2_CREDIT_ADD  TRC_SCHED_CLASS + 4
-#define TRC_CSCHED2_TICKLE_CHECK TRC_SCHED_CLASS + 5
-#define TRC_CSCHED2_TICKLE       TRC_SCHED_CLASS + 6
-#define TRC_CSCHED2_CREDIT_RESET TRC_SCHED_CLASS + 7
-#define TRC_CSCHED2_SCHED_TASKLET TRC_SCHED_CLASS + 8
-#define TRC_CSCHED2_UPDATE_LOAD   TRC_SCHED_CLASS + 9
-#define TRC_CSCHED2_RUNQ_ASSIGN   TRC_SCHED_CLASS + 10
-#define TRC_CSCHED2_UPDATE_VCPU_LOAD   TRC_SCHED_CLASS + 11
-#define TRC_CSCHED2_UPDATE_RUNQ_LOAD   TRC_SCHED_CLASS + 12
+/*
+ * Credit2 tracing events ("only" 512 available!). Check
+ * include/public/trace.h for more details.
+ */
+#define TRC_CSCHED2_EVENT(_e)        ((TRC_SCHED_CLASS|TRC_MASK_CSCHED2) + _e)

I think I would make this generic, and put it in trace.h -- maybe something like this?  (Haven't run this through a compiler)

#define TRC_SCHED_CLASS_EVT(_c, _e) \
  ((TRC_SCHED_CLASS|(TRC_SCHED_##_c<<TRC_SCHED_MASK_SHIFT))+(_e&TRC_SCHED_CLASS_MASK))

Then these would look like:
#define TRC_CSCHED2_TICK TRC_SCHED_CLASS_EVT(CSCHED2,1)
 

+
+#define TRC_CSCHED2_TICK             (TRC_CSCHED2_EVENT(1))
+#define TRC_CSCHED2_RUNQ_POS         (TRC_CSCHED2_EVENT(2))
+#define TRC_CSCHED2_CREDIT_BURN      (TRC_CSCHED2_EVENT(3))
+#define TRC_CSCHED2_CREDIT_ADD       (TRC_CSCHED2_EVENT(4))
+#define TRC_CSCHED2_TICKLE_CHECK     (TRC_CSCHED2_EVENT(5))
+#define TRC_CSCHED2_TICKLE           (TRC_CSCHED2_EVENT(6))
+#define TRC_CSCHED2_CREDIT_RESET     (TRC_CSCHED2_EVENT(7))
+#define TRC_CSCHED2_SCHED_TASKLET    (TRC_CSCHED2_EVENT(8))
+#define TRC_CSCHED2_UPDATE_LOAD      (TRC_CSCHED2_EVENT(9))
+#define TRC_CSCHED2_RUNQ_ASSIGN      (TRC_CSCHED2_EVENT(10))
+#define TRC_CSCHED2_UPDATE_VCPU_LOAD (TRC_CSCHED2_EVENT(11))
+#define TRC_CSCHED2_UPDATE_RUNQ_LOAD (TRC_CSCHED2_EVENT(12))

 /*
  * WARNING: This is still in an experimental phase.  Status and work can be found at the
diff --git a/xen/include/public/trace.h b/xen/include/public/trace.h
--- a/xen/include/public/trace.h
+++ b/xen/include/public/trace.h
@@ -57,6 +57,26 @@
 #define TRC_SCHED_CLASS     0x00022000   /* Scheduler-specific    */
 #define TRC_SCHED_VERBOSE   0x00028000   /* More inclusive scheduling */

+/*
+ * Per-scheduler masks, to identify scheduler specific events.
+ *
+ * The highest 3 bits of the last 12 bits of the above TRC_SCHED_*
+ * tracing classes are reserved for encoding what scheduler is producing
+ * the event. The last 9 bits is where the scheduler specific event is
+ * encoded.
+ *
+ * This means we can have at most 8 tracing scheduling masks (which
+ * means at most 8 schedulers generating tracing events) and, in each
+ * scheduler, up to 512 different events.
+ */
+#define TRC_SCHED_ID_BITS    3
+#define TRC_SCHED_MASK_SHIFT (TRC_SUBCLS_SHIFT - TRC_SCHED_ID_BITS)
+
+#define TRC_MASK_CSCHED      (0 << TRC_SCHED_MASK_SHIFT)
+#define TRC_MASK_CSCHED2     (1 << TRC_SCHED_MASK_SHIFT)
+#define TRC_MASK_SEDF        (2 << TRC_SCHED_MASK_SHIFT)
+#define TRC_MASK_ARINC653    (3 << TRC_SCHED_MASK_SHIFT)

I don't think "mask" is right here -- these aren't masks, they're numerical values. :-)  If we use something like the #define above, then we can do:

#define TRC_SCHED_CSCHED 0
#define TRC_SCHED_CSCHED2
/*...*/
 
 -George

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