psi: Introduce ftrace events

Add ftrace events to capture per-zone memory stats when a
trigger threshold is hit.

Change-Id: Ic52a27713acd34090c8f99543408b277877015c7
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>

include/trace/events/psi.h

@@ -0,0 +1,70 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) 2019, The Linux Foundation. All rights reserved.
+ */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM psi
+
+#if !defined(_TRACE_PSI_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_PSI_H
+
+#include <linux/types.h>
+#include <linux/tracepoint.h>
+#include <linux/psi_types.h>
+
+TRACE_EVENT(psi_window_vmstat,
+
+	TP_PROTO(u64 memstall, const char *zone_name, u64 high,
+		u64 free, u64 cma, u64 file),
+
+	TP_ARGS(memstall, zone_name, high, free, cma, file),
+
+	TP_STRUCT__entry(
+		__field(u64, memstall)
+		__string(name, zone_name)
+		__field(u64, high)
+		__field(u64, free)
+		__field(u64, cma)
+		__field(u64, file)
+	),
+
+	TP_fast_assign(
+		__entry->memstall = memstall;
+		__assign_str(name, zone_name);
+		__entry->high = high;
+		__entry->free = free;
+		__entry->cma = cma;
+		__entry->file = file;
+	),
+
+	TP_printk("%16s: Memstall: %#16llx High: %#8llx Free: %#8llx CMA: %#8llx File: %#8llx",
+		__get_str(name), __entry->memstall,  __entry->high,
+		__entry->free, __entry->cma, __entry->file
+	)
+);
+
+TRACE_EVENT(psi_event,
+
+	TP_PROTO(enum psi_states state, u64 threshold),
+
+	TP_ARGS(state, threshold),
+
+	TP_STRUCT__entry(
+		__field(enum psi_states, state)
+		__field(u64, threshold)
+	),
+
+	TP_fast_assign(
+		__entry->state = state;
+		__entry->threshold = threshold;
+	),
+
+	TP_printk("State: %d Threshold: %#llx",
+		__entry->state, __entry->threshold
+	)
+);
+
+#endif
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>

init/Kconfig

@@ -532,6 +532,16 @@ config PSI_DEFAULT_DISABLED
 	  per default but can be enabled through passing psi_enable=1
 	  on the kernel commandline during boot.
 
+config PSI_FTRACE
+	bool "Insert debug hooks for PSI ftrace events"
+	default n
+	depends on PSI
+	help
+	  If not set, PSI ftrace events will be disabled and
+	  will not incur any performance penalty.
+	  If set, PSI ftrace events may be
+	  enabled.
+
 endmenu # "CPU/Task time and stats accounting"
 
 config CPU_ISOLATION

kernel/sched/psi.c

@@ -142,6 +142,9 @@
 #include <linux/psi.h>
 #include "sched.h"
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/psi.h>
+
 static int psi_bug __read_mostly;
 
 DEFINE_STATIC_KEY_FALSE(psi_disabled);
@@ -441,6 +444,33 @@ static void psi_avgs_work(struct work_struct *work)
 	mutex_unlock(&group->avgs_lock);
 }
 
+#ifdef CONFIG_PSI_FTRACE
+static void trace_event_helper(struct psi_group *group)
+{
+	struct zone *zone;
+	unsigned long wmark;
+	unsigned long free;
+	unsigned long cma;
+	unsigned long file;
+	u64 memstall = group->total[PSI_POLL][PSI_MEM_SOME];
+
+	for_each_populated_zone(zone) {
+		wmark = zone->watermark[WMARK_HIGH];
+		free = zone_page_state(zone, NR_FREE_PAGES);
+		cma = zone_page_state(zone, NR_FREE_CMA_PAGES);
+		file = zone_page_state(zone, NR_ZONE_ACTIVE_FILE) +
+			zone_page_state(zone, NR_ZONE_INACTIVE_FILE);
+
+		trace_psi_window_vmstat(
+			memstall, zone->name, wmark, free, cma, file);
+	}
+}
+#else
+static void trace_event_helper(struct psi_group *group)
+{
+}
+#endif /* CONFIG_PSI_FTRACE */
+
 /* Trigger tracking window manupulations */
 static void window_reset(struct psi_window *win, u64 now, u64 value,
 			 u64 prev_growth)
@@ -533,6 +563,8 @@ static u64 update_triggers(struct psi_group *group, u64 now)
 		if (now < t->last_event_time + t->win.size)
 			continue;
 
+		trace_psi_event(t->state, t->threshold);
+
 		/* Generate an event */
 		if (cmpxchg(&t->event, 0, 1) == 0)
 			wake_up_interruptible(&t->event_wait);
@@ -605,6 +637,7 @@ static void psi_poll_work(struct kthread_work *work)
 		 */
 		group->polling_until = now +
 			group->poll_min_period * UPDATES_PER_WINDOW;
+		trace_event_helper(group);
 	}
 
 	if (now > group->polling_until) {