From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934536AbdBQQPl (ORCPT ); Fri, 17 Feb 2017 11:15:41 -0500 Received: from gum.cmpxchg.org ([85.214.110.215]:35844 "EHLO gum.cmpxchg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934088AbdBQQPj (ORCPT ); Fri, 17 Feb 2017 11:15:39 -0500 Date: Fri, 17 Feb 2017 11:15:32 -0500 From: Johannes Weiner To: Minchan Kim Cc: Shaohua Li , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Kernel-team@fb.com, mhocko@suse.com, hughd@google.com, riel@redhat.com, mgorman@techsingularity.net, akpm@linux-foundation.org Subject: Re: [PATCH V3 3/7] mm: reclaim MADV_FREE pages Message-ID: <20170217161532.GC23735@cmpxchg.org> References: <20170216184018.GC20791@cmpxchg.org> <20170217054108.GA3653@bbox> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170217054108.GA3653@bbox> User-Agent: Mutt/1.7.2 (2016-11-26) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Feb 17, 2017 at 02:41:08PM +0900, Minchan Kim wrote: > Hi Johannes, > > On Thu, Feb 16, 2017 at 01:40:18PM -0500, Johannes Weiner wrote: > > On Tue, Feb 14, 2017 at 11:36:09AM -0800, Shaohua Li wrote: > > > @@ -911,7 +911,7 @@ static void page_check_dirty_writeback(struct page *page, > > > * Anonymous pages are not handled by flushers and must be written > > > * from reclaim context. Do not stall reclaim based on them > > > */ > > > - if (!page_is_file_cache(page)) { > > > + if (!page_is_file_cache(page) || page_is_lazyfree(page)) { > > > > Do we need this? MADV_FREE clears the dirty bit off the page; we could > > just let them go through with the function without any special-casing. > > I thought some driver potentially can do GUP with FOLL_TOUCH so that the > lazyfree page can have PG_dirty with !PG_swapbacked. In this case, > throttling logic of shrink_page_list can be confused? Yep, agreed. We should filter these pages here. > > > @@ -1142,7 +1144,7 @@ static unsigned long shrink_page_list(struct list_head *page_list, > > > * The page is mapped into the page tables of one or more > > > * processes. Try to unmap it here. > > > */ > > > - if (page_mapped(page) && mapping) { > > > + if (page_mapped(page) && (mapping || lazyfree)) { > > > > Do we actually need to filter for mapping || lazyfree? If we fail to > > allocate swap, we don't reach here. If the page is a truncated file > > page, ttu returns pretty much instantly with SWAP_AGAIN. We should be > > able to just check for page_mapped() alone, no? > > try_to_unmap_one assumes every anonymous pages reached will have swp_entry > so it should be changed to check PageSwapCache if we go to the way. Yep, I think it should check page_mapping(). To me that would make the most sense, see other email: "Don't unmap a ram page with valid data when there is no secondary storage mapping to maintain integrity."