Messages in this thread Patch in this message |  | | | Date | Wed, 25 May 2011 12:13:28 +0900 | | From | KOSAKI Motohiro <> | | Subject | [PATCH 3/3] swap-token: add a comment for priority aging |
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Add to a few comment of design decision of swap token aging.
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> --- mm/thrash.c | 11 +++++++++++ 1 files changed, 11 insertions(+), 0 deletions(-) diff --git a/mm/thrash.c b/mm/thrash.c index 0504e8a..8832edb 100644 --- a/mm/thrash.c +++ b/mm/thrash.c @@ -50,6 +50,17 @@ 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; -- 1.7.3.1
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