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So that it becomes possible to create scheduler specific trace records,
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@citrix.com>
---
Changes from v1:
* The event ID generaion macro is now called `TRC_SCHED_CLASS_EVT()',
and has been generalized and put in trace.h, as suggested.
* The handling of per-scheduler tracing IDs and masks have been
restructured, properly naming "ID" the numerical identifiers
and "MASK" the bitmasks, as requested.

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 +29,22 @@
#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_TICK TRC_SCHED_CLASS_EVT(CSCHED2, 1)
+#define TRC_CSCHED2_RUNQ_POS TRC_SCHED_CLASS_EVT(CSCHED2, 2)
+#define TRC_CSCHED2_CREDIT_BURN TRC_SCHED_CLASS_EVT(CSCHED2, 3)
+#define TRC_CSCHED2_CREDIT_ADD TRC_SCHED_CLASS_EVT(CSCHED2, 4)
+#define TRC_CSCHED2_TICKLE_CHECK TRC_SCHED_CLASS_EVT(CSCHED2, 5)
+#define TRC_CSCHED2_TICKLE TRC_SCHED_CLASS_EVT(CSCHED2, 6)
+#define TRC_CSCHED2_CREDIT_RESET TRC_SCHED_CLASS_EVT(CSCHED2, 7)
+#define TRC_CSCHED2_SCHED_TASKLET TRC_SCHED_CLASS_EVT(CSCHED2, 8)
+#define TRC_CSCHED2_UPDATE_LOAD TRC_SCHED_CLASS_EVT(CSCHED2, 9)
+#define TRC_CSCHED2_RUNQ_ASSIGN TRC_SCHED_CLASS_EVT(CSCHED2, 10)
+#define TRC_CSCHED2_UPDATE_VCPU_LOAD TRC_SCHED_CLASS_EVT(CSCHED2, 11)
+#define TRC_CSCHED2_UPDATE_RUNQ_LOAD TRC_SCHED_CLASS_EVT(CSCHED2, 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 +57,32 @@
#define TRC_SCHED_CLASS 0x00022000 /* Scheduler-specific */
#define TRC_SCHED_VERBOSE 0x00028000 /* More inclusive scheduling */

+/*
+ * The highest 3 bits of the last 12 bits of TRC_SCHED_CLASS above are
+ * reserved for encoding what scheduler produced the information. The
+ * actual event is encoded in the last 9 bits.
+ *
+ * This means we have 8 scheduling IDs available (which means at most 8
+ * schedulers generating events) and, in each scheduler, up to 512
+ * different events.
+ */
+#define TRC_SCHED_ID_BITS 3
+#define TRC_SCHED_ID_SHIFT (TRC_SUBCLS_SHIFT - TRC_SCHED_ID_BITS)
+#define TRC_SCHED_ID_MASK (((1UL<<TRC_SCHED_ID_BITS) - 1) << TRC_SCHED_ID_SHIFT)
+#define TRC_SCHED_EVT_MASK (~(TRC_SCHED_ID_MASK))
+
+/* Per-scheduler IDs, to identify scheduler specific events */
+#define TRC_SCHED_CSCHED 0
+#define TRC_SCHED_CSCHED2 1
+#define TRC_SCHED_SEDF 2
+#define TRC_SCHED_ARINC653 3
+
+/* Per-scheduler tracing */
+#define TRC_SCHED_CLASS_EVT(_c, _e) \
+ ( ( TRC_SCHED_CLASS | \
+ ((TRC_SCHED_##_c << TRC_SCHED_ID_SHIFT) & TRC_SCHED_ID_MASK) ) + \
+ (_e & TRC_SCHED_EVT_MASK) )
+
/* Trace classes for Hardware */
#define TRC_HW_PM 0x00801000 /* Power management traces */
#define TRC_HW_IRQ 0x00802000 /* Traces relating to the handling of IRQs */

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