From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 15 Jan 2008 08:57:11 +0900 From: KOSAKI Motohiro Subject: Re: [patch 05/19] split LRU lists into anon & file sets In-Reply-To: <20080111104651.3ebea5ea@bree.surriel.com> References: <20080111162320.FD6A.KOSAKI.MOTOHIRO@jp.fujitsu.com> <20080111104651.3ebea5ea@bree.surriel.com> Message-Id: <20080115084534.116A.KOSAKI.MOTOHIRO@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Rik van Riel Cc: kosaki.motohiro@jp.fujitsu.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Lee Schermerhorn List-ID: Hi > > Why drop (total_swap_pages == 0 && PageAnon(page)) condition? > > in embedded sysmtem, > > CONFIG_NORECLAIM is OFF (because almost embedded cpu is 32bit) and > > that anon move to inactive list is meaningless because it doesn't have swap. > > That was a mistake, kind of. Since all swap backed pages are on their > own LRU lists, we should not scan those lists at all any more if we are > out of swap space. > > The patch that fixes get_scan_ratio() adds that test. > > Having said that, with the nr_swap_pages==0 test in get_scan_ratio(), > we no longer need to test for that condition in shrink_active_list(). Oh I see! thank you for your kindful lecture. your implementation is very cute. > > below code is more good, may be. > > but I don't understand yet why ignore page_referenced() result at anon page ;-) > > On modern systems, swapping out anonymous pages is a relatively rare > event. All anonymous pages start out as active and referenced, so > testing for that condition does (1) not add any information and (2) > mean we need to scan ALL of the anonymous pages, in order to find one > candidate to swap out (since they are all referenced). > > Simply deactivating a few pages and checking whether they were referenced > again while on the (smaller) inactive_anon_list means we can find candidates > to page out with a lot less CPU time used. thanks, I understand, may be. - kosaki -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org