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>

1 files changed, 10 insertions, 1 deletions

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;
                 }