vmscan: implement swap token trace

This is useful for observing swap token activity.

example output:

             zsh-1845  [000]   598.962716: update_swap_token_priority:
mm=ffff88015eaf7700 old_prio=1 new_prio=0
          memtoy-1830  [001]   602.033900: update_swap_token_priority:
mm=ffff880037a45880 old_prio=947 new_prio=949
          memtoy-1830  [000]   602.041509: update_swap_token_priority:
mm=ffff880037a45880 old_prio=949 new_prio=951
          memtoy-1830  [000]   602.051959: update_swap_token_priority:
mm=ffff880037a45880 old_prio=951 new_prio=953
          memtoy-1830  [000]   602.052188: update_swap_token_priority:
mm=ffff880037a45880 old_prio=953 new_prio=955
          memtoy-1830  [001]   602.427184: put_swap_token:
token_mm=ffff880037a45880
             zsh-1789  [000]   602.427281: replace_swap_token:
old_token_mm=          (null) old_prio=0 new_token_mm=ffff88015eaf7018
new_prio=2
             zsh-1789  [001]   602.433456: update_swap_token_priority:
mm=ffff88015eaf7018 old_prio=2 new_prio=4
             zsh-1789  [000]   602.437613: update_swap_token_priority:
mm=ffff88015eaf7018 old_prio=4 new_prio=6
             zsh-1789  [000]   602.443924: update_swap_token_priority:
mm=ffff88015eaf7018 old_prio=6 new_prio=8
             zsh-1789  [000]   602.451873: update_swap_token_priority:
mm=ffff88015eaf7018 old_prio=8 new_prio=10
             zsh-1789  [001]   602.462639: update_swap_token_priority:
mm=ffff88015eaf7018 old_prio=10 new_prio=12
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: Rik van Riel<riel@redhat.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/trace/events/vmscan.h

@@ -6,6 +6,8 @@
 
 #include <linux/types.h>
 #include <linux/tracepoint.h>
+#include <linux/mm.h>
+#include <linux/memcontrol.h>
 #include "gfpflags.h"
 
 #define RECLAIM_WB_ANON		0x0001u
@@ -310,6 +312,81 @@ TRACE_EVENT(mm_vmscan_lru_shrink_inactive,
 		show_reclaim_flags(__entry->reclaim_flags))
 );
 
+TRACE_EVENT(replace_swap_token,
+	TP_PROTO(struct mm_struct *old_mm,
+		 struct mm_struct *new_mm),
+
+	TP_ARGS(old_mm, new_mm),
+
+	TP_STRUCT__entry(
+		__field(struct mm_struct*,	old_mm)
+		__field(unsigned int,		old_prio)
+		__field(struct mm_struct*,	new_mm)
+		__field(unsigned int,		new_prio)
+	),
+
+	TP_fast_assign(
+		__entry->old_mm   = old_mm;
+		__entry->old_prio = old_mm ? old_mm->token_priority : 0;
+		__entry->new_mm   = new_mm;
+		__entry->new_prio = new_mm->token_priority;
+	),
+
+	TP_printk("old_token_mm=%p old_prio=%u new_token_mm=%p new_prio=%u",
+		  __entry->old_mm, __entry->old_prio,
+		  __entry->new_mm, __entry->new_prio)
+);
+
+DECLARE_EVENT_CLASS(put_swap_token_template,
+	TP_PROTO(struct mm_struct *swap_token_mm),
+
+	TP_ARGS(swap_token_mm),
+
+	TP_STRUCT__entry(
+		__field(struct mm_struct*, swap_token_mm)
+	),
+
+	TP_fast_assign(
+		__entry->swap_token_mm = swap_token_mm;
+	),
+
+	TP_printk("token_mm=%p", __entry->swap_token_mm)
+);
+
+DEFINE_EVENT(put_swap_token_template, put_swap_token,
+	TP_PROTO(struct mm_struct *swap_token_mm),
+	TP_ARGS(swap_token_mm)
+);
+
+DEFINE_EVENT_CONDITION(put_swap_token_template, disable_swap_token,
+	TP_PROTO(struct mm_struct *swap_token_mm),
+	TP_ARGS(swap_token_mm),
+	TP_CONDITION(swap_token_mm != NULL)
+);
+
+TRACE_EVENT_CONDITION(update_swap_token_priority,
+	TP_PROTO(struct mm_struct *mm,
+		 unsigned int old_prio),
+
+	TP_ARGS(mm, old_prio),
+
+	TP_CONDITION(mm->token_priority != old_prio),
+
+	TP_STRUCT__entry(
+		__field(struct mm_struct*, mm)
+		__field(unsigned int, old_prio)
+		__field(unsigned int, new_prio)
+	),
+
+	TP_fast_assign(
+		__entry->mm = mm;
+		__entry->old_prio = old_prio;
+		__entry->new_prio = mm->token_priority;
+	),
+
+	TP_printk("mm=%p old_prio=%u new_prio=%u",
+		  __entry->mm, __entry->old_prio, __entry->new_prio)
+);
 
 #endif /* _TRACE_VMSCAN_H */
 

mm/thrash.c

@@ -23,6 +23,8 @@
 #include <linux/swap.h>
 #include <linux/memcontrol.h>
 
+#include <trace/events/vmscan.h>
+
 static DEFINE_SPINLOCK(swap_token_lock);
 struct mm_struct *swap_token_mm;
 struct mem_cgroup *swap_token_memcg;
@@ -49,6 +51,7 @@ static struct mem_cgroup *swap_token_memcg_from_mm(struct mm_struct *mm)
 void grab_swap_token(struct mm_struct *mm)
 {
 	int current_interval;
+	unsigned int old_prio = mm->token_priority;
 
 	global_faults++;
 
@@ -63,7 +66,7 @@ void grab_swap_token(struct mm_struct *mm)
 
 	if (mm == swap_token_mm) {
 		mm->token_priority += 2;
-		goto out;
+		goto update_priority;
 	}
 
 	if (current_interval < mm->last_interval)
@@ -77,6 +80,9 @@ void grab_swap_token(struct mm_struct *mm)
 	if (mm->token_priority > swap_token_mm->token_priority)
 		goto replace_token;
 
+update_priority:
+	trace_update_swap_token_priority(mm, old_prio);
+
 out:
 	mm->faultstamp = global_faults;
 	mm->last_interval = current_interval;
@@ -85,6 +91,7 @@ void grab_swap_token(struct mm_struct *mm)
 
 replace_token:
 	mm->token_priority += 2;
+	trace_replace_swap_token(swap_token_mm, mm);
 	swap_token_mm = mm;
 	swap_token_memcg = swap_token_memcg_from_mm(mm);
 	goto out;
@@ -95,6 +102,7 @@ void __put_swap_token(struct mm_struct *mm)
 {
 	spin_lock(&swap_token_lock);
 	if (likely(mm == swap_token_mm)) {
+		trace_put_swap_token(swap_token_mm);
 		swap_token_mm = NULL;
 		swap_token_memcg = NULL;
 	}
@@ -118,6 +126,7 @@ void disable_swap_token(struct mem_cgroup *memcg)
 	if (match_memcg(memcg, swap_token_memcg)) {
 		spin_lock(&swap_token_lock);
 		if (match_memcg(memcg, swap_token_memcg)) {
+			trace_disable_swap_token(swap_token_mm);
 			swap_token_mm = NULL;
 			swap_token_memcg = NULL;
 		}