diff options
| author | KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> | 2011-07-25 17:12:08 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2011-07-25 20:57:08 -0700 |
| commit | 45ebb840257b060ec54416aebffd9747e210962c (patch) | |
| tree | 0236eba5f2f420dccae80f97a70192ef965d6f5f | |
| parent | 53bb01f593d50188c8d638f89db96f9b6b042bcd (diff) | |
mm: swap-token: add a comment for priority aging
Document some swap token aging design decisions.
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | mm/thrash.c | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/mm/thrash.c b/mm/thrash.c index 42ffb0179271..e53f7d02c17c 100644 --- a/mm/thrash.c +++ b/mm/thrash.c @@ -67,6 +67,17 @@ void grab_swap_token(struct mm_struct *mm) if (!swap_token_mm) goto replace_token; + /* + * Usually, we don't need priority aging because long interval faults + * makes priority decrease quickly. But there is one exception. If the + * token owner task is sleeping, it never make long interval faults. + * Thus, we need a priority aging mechanism instead. The requirements + * of priority aging are + * 1) An aging interval is reasonable enough long. Too short aging + * interval makes quick swap token lost and decrease performance. + * 2) The swap token owner task have to get priority aging even if + * it's under sleep. + */ if ((global_faults - last_aging) > TOKEN_AGING_INTERVAL) { swap_token_mm->token_priority /= 2; last_aging = global_faults; |