s390/hiperdispatch: Add trace events

Add trace events to debug hiperdispatch behavior and track domain
rebuilding. Two events provide information about the decision making of
hiperdispatch and the adjustments made.

Acked-by: Vasily Gorbik <[e-mail]>
Co-developed-by: Tobias Huschle <[e-mail]>
Signed-off-by: Tobias Huschle <[e-mail]>
Signed-off-by: Mete Durlu <[e-mail]>
Signed-off-by: Vasily Gorbik <[e-mail]>

arch/s390/include/asm/trace/hiperdispatch.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Tracepoint header for hiperdispatch
+ *
+ * Copyright IBM Corp. 2024
+ */
+
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM s390
+
+#if !defined(_TRACE_S390_HIPERDISPATCH_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_S390_HIPERDISPATCH_H
+
+#include <linux/tracepoint.h>
+
+#undef TRACE_INCLUDE_PATH
+#undef TRACE_INCLUDE_FILE
+
+#define TRACE_INCLUDE_PATH asm/trace
+#define TRACE_INCLUDE_FILE hiperdispatch
+
+TRACE_EVENT(s390_hd_work_fn,
+	    TP_PROTO(int steal_time_percentage,
+		     int entitled_core_count,
+		     int highcap_core_count),
+	    TP_ARGS(steal_time_percentage,
+		    entitled_core_count,
+		    highcap_core_count),
+	    TP_STRUCT__entry(__field(int, steal_time_percentage)
+			     __field(int, entitled_core_count)
+			     __field(int, highcap_core_count)),
+	    TP_fast_assign(__entry->steal_time_percentage = steal_time_percentage;
+			   __entry->entitled_core_count = entitled_core_count;
+			   __entry->highcap_core_count = highcap_core_count;),
+	    TP_printk("steal: %d entitled_core_count: %d highcap_core_count: %d",
+		      __entry->steal_time_percentage,
+		      __entry->entitled_core_count,
+		      __entry->highcap_core_count)
+);
+
+TRACE_EVENT(s390_hd_rebuild_domains,
+	    TP_PROTO(int current_highcap_core_count,
+		     int new_highcap_core_count),
+	    TP_ARGS(current_highcap_core_count,
+		    new_highcap_core_count),
+	    TP_STRUCT__entry(__field(int, current_highcap_core_count)
+			     __field(int, new_highcap_core_count)),
+	    TP_fast_assign(__entry->current_highcap_core_count = current_highcap_core_count;
+			   __entry->new_highcap_core_count = new_highcap_core_count),
+	    TP_printk("change highcap_core_count: %u -> %u",
+		      __entry->current_highcap_core_count,
+		      __entry->new_highcap_core_count)
+);
+
+#endif /* _TRACE_S390_HIPERDISPATCH_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>

arch/s390/kernel/hiperdispatch.c

···
 #include <asm/smp.h>
 #include <asm/topology.h>
 
+#define CREATE_TRACE_POINTS
+#include <asm/trace/hiperdispatch.h>
+
 #define HD_DELAY_FACTOR			(4)
 #define HD_DELAY_INTERVAL		(HZ / 4)
 #define HD_STEAL_THRESHOLD		30
···
 	else
 		new_cores = hd_entitled_cores;
 	if (hd_high_capacity_cores != new_cores) {
+		trace_s390_hd_rebuild_domains(hd_high_capacity_cores, new_cores);
 		hd_high_capacity_cores = new_cores;
 		topology_schedule_update();
 	}
+	trace_s390_hd_work_fn(steal_percentage, hd_entitled_cores, hd_high_capacity_cores);
 	mutex_unlock(&smp_cpu_state_mutex);
 	schedule_delayed_work(&hd_capacity_work, HD_DELAY_INTERVAL);
 }