From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 17 Sep 2008 14:46:59 +0900 From: KAMEZAWA Hiroyuki Subject: Re: [PATCH -mm] memcg: fix handling of shmem migration Message-Id: <20080917144659.2e363edc.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20080917133149.b012a1c2.nishimura@mxp.nes.nec.co.jp> References: <20080917133149.b012a1c2.nishimura@mxp.nes.nec.co.jp> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Daisuke Nishimura Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, balbir@linux.vnet.ibm.com, xemul@openvz.org List-ID: On Wed, 17 Sep 2008 13:31:49 +0900 Daisuke Nishimura wrote: > PG_swapbacked flag of newpage should be set(if needed) before > mem_cgroup_prepare_migration, because mem_cgroup_charge_common > checks the flag and determines whether it sets PAGE_CGROUP_FLAG_FILE or not. > > Before this patch, if migrating shmem/tmpfs pages, newpage would be > charged with PAGE_CGROUP_FLAG_FILE set, while oldpage has been charged > without the flag. > Nice catch ! Thank you. Hmm, should I add MEM_CGROUP_CHARGE_TYPE_SHMEM rather than setting flag to newpage ? Acked-by: KAMEZAWA Hiroyuki > The problem here is mem_cgroup_move_lists doesn't clear(or set) > the PAGE_CGROUP_FLAG_FILE flag, so pc->flags of the newpage > remains PAGE_CGROUP_FLAG_FILE set even when the pc is moved to > another lru(anon) by mem_cgroup_move_lists. And this leads to > incorrect MEM_CGROUP_ZSTAT. > (In my test, I see an underflow of MEM_CGROUP_ZSTAT(active_file). > As a result, mem_cgroup_calc_reclaim returns very huge number and > causes soft lockup on page reclaim.) > > I'm not sure if mem_cgroup_move_lists should handle PAGE_CGROUP_FLAG_FILE > or not(I suppose it should be used to move between active <-> inactive, > not anon <-> file), I moved SetPageSwapBacked(newpage) before > mem_cgroup_prepare_migration. > > > Signed-off-by: Daisuke Nishimura > --- > mm/migrate.c | 4 ++-- > 1 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/migrate.c b/mm/migrate.c > index 577d481..7343463 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -586,8 +586,6 @@ static int move_to_new_page(struct page *newpage, struct page *page) > /* Prepare mapping for the new page.*/ > newpage->index = page->index; > newpage->mapping = page->mapping; > - if (PageSwapBacked(page)) > - SetPageSwapBacked(newpage); > > mapping = page_mapping(page); > if (!mapping) > @@ -636,6 +634,8 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private, > goto move_newpage; > } > > + if (PageSwapBacked(page)) > + SetPageSwapBacked(newpage); > charge = mem_cgroup_prepare_migration(page, newpage); > if (charge == -ENOMEM) { > rc = -ENOMEM; > -- 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