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Commit 45ebb840 authored by KOSAKI Motohiro's avatar KOSAKI Motohiro Committed by Linus Torvalds
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mm: swap-token: add a comment for priority aging 



Document some swap token aging design decisions.

Signed-off-by: default avatarKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: default avatarRik van Riel <riel@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 53bb01f5

mm/thrash.c

+11 −0
Original line number Diff line number Diff line
@@ -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;