mm: swap-token: add a comment for priority aging (45ebb840) · Commits · 戴 / test

Document some swap token aging design decisions. Signed-off-by:

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;