vmscan: implement swap token priority aging

While testing for memcg aware swap token, I observed a swap token was
often grabbed an intermittent running process (eg init, auditd) and they
never release a token.

Why?

Some processes (eg init, auditd, audispd) wake up when a process exiting.
And swap token can be get first page-in process when a process exiting
makes no swap token owner.  Thus such above intermittent running process
often get a token.

And currently, swap token priority is only decreased at page fault path.
Then, if the process sleep immediately after to grab swap token, the swap
token priority never be decreased.  That's obviously undesirable.

This patch implement very poor (and lightweight) priority aging.  It only
be affect to the above corner case and doesn't change swap tendency
workload performance (eg multi process qsbench load)

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-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, 13 insertions, 7 deletions

diff --git a/include/trace/events/vmscan.h b/include/trace/events/vmscan.h
index 1798e0cee2a..b2c33bd955f 100644
--- a/include/trace/events/vmscan.h
+++ b/include/trace/events/vmscan.h
@@ -366,9 +366,10 @@ DEFINE_EVENT_CONDITION(put_swap_token_template, disable_swap_token,
 
 TRACE_EVENT_CONDITION(update_swap_token_priority,
         TP_PROTO(struct mm_struct *mm,
-                 unsigned int old_prio),
+                 unsigned int old_prio,
+                 struct mm_struct *swap_token_mm),
 
-        TP_ARGS(mm, old_prio),
+        TP_ARGS(mm, old_prio, swap_token_mm),
 
         TP_CONDITION(mm->token_priority != old_prio),
 
@@ -376,16 +377,21 @@ TRACE_EVENT_CONDITION(update_swap_token_priority,
                 __field(struct mm_struct*, mm)
                 __field(unsigned int, old_prio)
                 __field(unsigned int, new_prio)
+                __field(struct mm_struct*, swap_token_mm)
+                __field(unsigned int, swap_token_prio)
         ),
 
         TP_fast_assign(
-                __entry->mm = mm;
-                __entry->old_prio = old_prio;
-                __entry->new_prio = mm->token_priority;
+                __entry->mm             = mm;
+                __entry->old_prio       = old_prio;
+                __entry->new_prio       = mm->token_priority;
+                __entry->swap_token_mm  = swap_token_mm;
+                __entry->swap_token_prio = swap_token_mm ? swap_token_mm->token_priority : 0;
         ),
 
-        TP_printk("mm=%p old_prio=%u new_prio=%u",
-                  __entry->mm, __entry->old_prio, __entry->new_prio)
+        TP_printk("mm=%p old_prio=%u new_prio=%u swap_token_mm=%p token_prio=%u",
+                  __entry->mm, __entry->old_prio, __entry->new_prio,
+                  __entry->swap_token_mm, __entry->swap_token_prio)
 );
 
 #endif /* _TRACE_VMSCAN_H */