From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with ESMTP id D2782900194 for ; Thu, 23 Jun 2011 18:06:44 -0400 (EDT) Received: by qwa26 with SMTP id 26so1587157qwa.14 for ; Thu, 23 Jun 2011 15:06:42 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <1308810981-5286-1-git-send-email-andrea@betterlinux.com> References: <1308810981-5286-1-git-send-email-andrea@betterlinux.com> Date: Fri, 24 Jun 2011 07:06:42 +0900 Message-ID: Subject: Re: [PATCH v2] fadvise: move active pages to inactive list with POSIX_FADV_DONTNEED From: Minchan Kim Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: Andrea Righi Cc: Andrew Morton , Rik van Riel , Peter Zijlstra , Johannes Weiner , KAMEZAWA Hiroyuki , Andrea Arcangeli , Hugh Dickins , Jerry James , Marcus Sorensen , Matt Heaton , KOSAKI Motohiro , linux-mm , LKML Hi Andrea, Sorry for late response. These day, I have no time to see the LKML. On Thu, Jun 23, 2011 at 3:36 PM, Andrea Righi wrot= e: > There were some reported problems in the past about trashing page cache > when a backup software (i.e., rsync) touches a huge amount of pages (see > for example [1]). > > This problem has been almost fixed by the Minchan Kim's patch [2] and a > proper use of fadvise() in the backup software. For example this patch > set [3] has been proposed for inclusion in rsync. > > However, there can be still other similar trashing problems: when the > backup software reads all the source files, some of them may be part of > the actual working set of the system. When a > posix_fadvise(POSIX_FADV_DONTNEED) is performed _all_ pages are evicted > from pagecache, both the working set and the use-once pages touched only > by the backup software. Agreed. It's rather aggressive. > > With the following solution when posix_fadvise(POSIX_FADV_DONTNEED) is > called for an active page instead of removing it from the page cache it > is added to the tail of the inactive list. Otherwise, if it's already in > the inactive list the page is removed from the page cache. > > In this way if the backup was the only user of a page, that page will > be immediately removed from the page cache by calling > posix_fadvise(POSIX_FADV_DONTNEED). If the page was also touched by > other processes it'll be moved to the inactive list, having another > chance of being re-added to the working set, or simply reclaimed when > memory is needed. > > Testcase: > > =C2=A0- create a 1GB file called "zero" > =C2=A0- run md5sum zero to read all the pages in page cache (this is to > =C2=A0 =C2=A0simulate the user activity on this file) > =C2=A0- run "rsync zero zero_copy" (rsync is patched with [3]) > =C2=A0- re-run md5sum zero (user activity on the working set) and measure > =C2=A0 =C2=A0the time to complete this command > > The test has been performed using 3.0.0-rc4 vanilla and with this patch > applied (3.0.0-rc4-fadvise). > > Results: > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0avg elapsed= time =C2=A0 =C2=A0 =C2=A0block:block_bio_queue > =C2=A03.0.0-rc4 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A04.127s =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0= =C2=A0 =C2=A08,214 > =C2=A03.0.0-rc4-fadvise =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A02.146s =C2=A0 = =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A00 > Great! > In the first case the file is evicted from page cache completely and we > must re-read it from the disk. In the second case the file is still in > page cache (in the inactive list) and we don't need any other additional > I/O operation. > > [1] http://marc.info/?l=3Drsync&m=3D128885034930933&w=3D2 > [2] https://lkml.org/lkml/2011/2/20/57 > [3] http://lists.samba.org/archive/rsync/2010-November/025827.html > > ChangeLog v1 -> v2: > =C2=A0- fix comment in invalidate_mapping_pages() > > Acked-by: Rik van Riel > Reviewed-by: KOSAKI Motohiro > Signed-off-by: Andrea Righi > --- > =C2=A0mm/swap.c =C2=A0 =C2=A0 | =C2=A0 =C2=A09 +++++---- > =C2=A0mm/truncate.c | =C2=A0 10 +++++++--- > =C2=A02 files changed, 12 insertions(+), 7 deletions(-) > > diff --git a/mm/swap.c b/mm/swap.c > index 3a442f1..fc8bb76 100644 > --- a/mm/swap.c > +++ b/mm/swap.c > @@ -411,10 +411,11 @@ void add_page_to_unevictable_list(struct page *page= ) > =C2=A0* > =C2=A0* 1. active, mapped page -> none > =C2=A0* 2. active, dirty/writeback page -> inactive, head, PG_reclaim > - * 3. inactive, mapped page -> none > - * 4. inactive, dirty/writeback page -> inactive, head, PG_reclaim > - * 5. inactive, clean -> inactive, tail > - * 6. Others -> none > + * 3. active, clean -> inactive, tail > + * 4. inactive, mapped page -> none > + * 5. inactive, dirty/writeback page -> inactive, head, PG_reclaim > + * 6. inactive, clean -> inactive, tail > + * 7. Others -> none Nitpick. I would like to put together them by on line as rather than adding another = line. 5, [in]active, clean-> inactive, tail. I guess it's more easy to understand. If you want to put it in another line, please change below comment, too. "In 5, why it moves inactive's head.." > =C2=A0* > =C2=A0* In 4, why it moves inactive's head, the VM expects the page would > =C2=A0* be write it out by flusher threads as this is much more effective > diff --git a/mm/truncate.c b/mm/truncate.c > index 3a29a61..a36af48 100644 > --- a/mm/truncate.c > +++ b/mm/truncate.c > @@ -357,11 +357,15 @@ unsigned long invalidate_mapping_pages(struct addre= ss_space *mapping, > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0if (lock_failed) > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0continue; > > - =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 ret =3D invalidate_inode_page(page); I would like to add comment. "Invalidation of active page is rather aggressive as we can't make sure it's not a working set of other processes. deactivate_page would move it into inactive's tail so the page will have a chance to activate again if other processes touch it. otherwise, it would be reclaimed simply". > + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 if (PageActive(page)) > + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 ret =3D 0; > + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 else > + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 ret =3D invalidate_inode_page(page); You have to change description of invalidate_mapping_pages. * invalidate_mapping_pages() will not block on IO activity. It will not * invalidate pages which are dirty, locked, under writeback, mapped into * pagetables or on active lru. > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0unlock_page(page); > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0/* > - =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0* Invalidation is a hint that the page is no longer > - =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0* of interest and try to speed up its reclaim. > + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0* Invalidation of an inactive page is a hint that the > + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0* page is no longer of interest and try to speed up > + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0* its reclaim. > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0 */ > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0if (!ret) > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0deactivate_page(page); > -- > 1.7.4.1 > > Otherwise, Looks good to me. Acked-by: Minchan Kim --=20 Kind regards, Minchan Kim -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org