From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wj0-f200.google.com (mail-wj0-f200.google.com [209.85.210.200]) by kanga.kvack.org (Postfix) with ESMTP id 9430E6B0038 for ; Wed, 4 Jan 2017 08:16:59 -0500 (EST) Received: by mail-wj0-f200.google.com with SMTP id hb5so115759203wjc.2 for ; Wed, 04 Jan 2017 05:16:59 -0800 (PST) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id u8si77644275wmd.98.2017.01.04.05.16.58 for (version=TLS1 cipher=AES128-SHA bits=128/128); Wed, 04 Jan 2017 05:16:58 -0800 (PST) Date: Wed, 4 Jan 2017 14:16:55 +0100 From: Michal Hocko Subject: Re: [PATCH 2/7] mm, vmscan: add active list aging tracepoint Message-ID: <20170104131653.GH25453@dhcp22.suse.cz> References: <20170104101942.4860-1-mhocko@kernel.org> <20170104101942.4860-3-mhocko@kernel.org> <646c3551-e794-611c-5247-490bd89133db@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <646c3551-e794-611c-5247-490bd89133db@suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Vlastimil Babka Cc: Andrew Morton , Mel Gorman , Johannes Weiner , Minchan Kim , Hillf Danton , linux-mm@kvack.org, LKML On Wed 04-01-17 13:52:24, Vlastimil Babka wrote: > On 01/04/2017 11:19 AM, Michal Hocko wrote: > > From: Michal Hocko > > > > Our reclaim process has several tracepoints to tell us more about how > > things are progressing. We are, however, missing a tracepoint to track > > active list aging. Introduce mm_vmscan_lru_shrink_active which reports > > the number of > > - nr_scanned, nr_taken pages to tell us the LRU isolation > > effectiveness. > > Well, this point is no longer true, is it... ups, leftover - nr_take - the number of isolated pages > > - nr_referenced pages which tells us that we are hitting referenced > > pages which are deactivated. If this is a large part of the > > reported nr_deactivated pages then we might be hitting into > > the active list too early because they might be still part of > > the working set. This might help to debug performance issues. > > - nr_activated pages which tells us how many pages are kept on the > > "nr_activated" is slightly misleading? They remain active, they are not > being activated (that's why the pgactivate vmstat is also not increased > on them, right?). I guess rename to "nr_active" ? Or something like > "nr_remain_active" although that's longer. will go with nr_active > > [...] > > > @@ -1857,6 +1859,7 @@ static void move_active_pages_to_lru(struct lruvec *lruvec, > > unsigned long pgmoved = 0; > > struct page *page; > > int nr_pages; > > + int nr_moved = 0; > > > > while (!list_empty(list)) { > > page = lru_to_page(list); > > @@ -1882,11 +1885,15 @@ static void move_active_pages_to_lru(struct lruvec *lruvec, > > spin_lock_irq(&pgdat->lru_lock); > > } else > > list_add(&page->lru, pages_to_free); > > + } else { > > + nr_moved += nr_pages; > > } > > } > > > > if (!is_active_lru(lru)) > > __count_vm_events(PGDEACTIVATE, pgmoved); > > So we now have pgmoved and nr_moved. One is used for vmstat, other for > tracepoint, and the only difference is that vmstat includes pages where > we raced with page being unmapped from all pte's (IIUC?) and thus > removed from lru, which should be rather rare? I guess those are being > counted into vmstat only due to how the code evolved from using pagevec. > If we don't consider them in the tracepoint, then I'd suggest we don't > count them into vmstat either, and simplify this. OK, but I would prefer to have this in a separate patch, OK? -- Michal Hocko SUSE Labs -- 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