Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759997Ab1FWWGp (ORCPT ); Thu, 23 Jun 2011 18:06:45 -0400 Received: from mail-qw0-f46.google.com ([209.85.216.46]:53239 "EHLO mail-qw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752913Ab1FWWGn convert rfc822-to-8bit (ORCPT ); Thu, 23 Jun 2011 18:06:43 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=w8P7bJkNzrjRwe3j53li+c7C05RPf4k/CTWnJuz+l2zn2PAlmzBcj7sRpRB62np1sd k5tetlkXoB0MMbFLBAoL+ZodWYXUmo3tPSqppLNiewq97WcyDHNtvlqk5unE6f7TKrQY LH149jyE0NSnBqCL+QVEbQfK8r24MGGfxC7JI= 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 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 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6444 Lines: 160 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 wrote: > 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: > >  - create a 1GB file called "zero" >  - run md5sum zero to read all the pages in page cache (this is to >    simulate the user activity on this file) >  - run "rsync zero zero_copy" (rsync is patched with [3]) >  - re-run md5sum zero (user activity on the working set) and measure >    the 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: >                  avg elapsed time      block:block_bio_queue >  3.0.0-rc4                  4.127s                      8,214 >  3.0.0-rc4-fadvise          2.146s                          0 > 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=rsync&m=128885034930933&w=2 > [2] https://lkml.org/lkml/2011/2/20/57 > [3] http://lists.samba.org/archive/rsync/2010-November/025827.html > > ChangeLog v1 -> v2: >  - fix comment in invalidate_mapping_pages() > > Acked-by: Rik van Riel > Reviewed-by: KOSAKI Motohiro > Signed-off-by: Andrea Righi > --- >  mm/swap.c     |    9 +++++---- >  mm/truncate.c |   10 +++++++--- >  2 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) >  * >  * 1. active, mapped page -> none >  * 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.." >  * >  * In 4, why it moves inactive's head, the VM expects the page would >  * 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 address_space *mapping, >                        if (lock_failed) >                                continue; > > -                       ret = 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". > +                       if (PageActive(page)) > +                               ret = 0; > +                       else > +                               ret = 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. >                        unlock_page(page); >                        /* > -                        * Invalidation is a hint that the page is no longer > -                        * of interest and try to speed up its reclaim. > +                        * Invalidation of an inactive page is a hint that the > +                        * page is no longer of interest and try to speed up > +                        * its reclaim. >                         */ >                        if (!ret) >                                deactivate_page(page); > -- > 1.7.4.1 > > Otherwise, Looks good to me. Acked-by: Minchan Kim -- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/