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>

2 files changed, 87 insertions, 1 deletions

diff --git a/include/trace/events/vmscan.h b/include/trace/events/vmscan.h
index ea422aaa23e1..1798e0cee2a9 100644
--- a/include/trace/events/vmscan.h
+++ b/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 */
 
diff --git a/mm/thrash.c b/mm/thrash.c
index 6cdf86511385..17d9e29e4c9c 100644
--- a/mm/thrash.c
+++ b/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 @@ out:
 
 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;
                 }