Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755005AbZC2Xpp (ORCPT ); Sun, 29 Mar 2009 19:45:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753643AbZC2Xpe (ORCPT ); Sun, 29 Mar 2009 19:45:34 -0400 Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:51823 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753116AbZC2Xpd (ORCPT ); Sun, 29 Mar 2009 19:45:33 -0400 From: KOSAKI Motohiro To: KAMEZAWA Hiroyuki Subject: Re: [PATCH] vmscan: memcg needs may_swap (Re: [patch] vmscan: rename sc.may_swap to may_unmap) Cc: kosaki.motohiro@jp.fujitsu.com, Daisuke Nishimura , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Johannes Weiner , MinChan Kim , Andrew Morton , "Rafael J. Wysocki" , Rik van Riel , Balbir Singh In-Reply-To: <20090327153035.35498303.kamezawa.hiroyu@jp.fujitsu.com> References: <20090327151926.f252fba7.nishimura@mxp.nes.nec.co.jp> <20090327153035.35498303.kamezawa.hiroyu@jp.fujitsu.com> Message-Id: <20090328214636.68FF.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Mailer: Becky! ver. 2.50 [ja] Date: Mon, 30 Mar 2009 08:45:28 +0900 (JST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5963 Lines: 177 > On Fri, 27 Mar 2009 15:19:26 +0900 > Daisuke Nishimura wrote: > > > Added > > Cc: KAMEZAWA Hiroyuki > > Cc: Balbir Singh > > > > I'm sorry for replying to a very old mail. > > > > > @@ -1713,7 +1713,7 @@ unsigned long try_to_free_mem_cgroup_pag > > > { > > > struct scan_control sc = { > > > .may_writepage = !laptop_mode, > > > - .may_swap = 1, > > > + .may_unmap = 1, > > > .swap_cluster_max = SWAP_CLUSTER_MAX, > > > .swappiness = swappiness, > > > .order = 0, > > > @@ -1723,7 +1723,7 @@ unsigned long try_to_free_mem_cgroup_pag > > > struct zonelist *zonelist; > > > > > > if (noswap) > > > - sc.may_swap = 0; > > > + sc.may_unmap = 0; > > > > > > sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | > > > (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); > > IIUC, memcg had used may_swap as a flag for "we need to use swap?" as the name indicate. > > > > Because, when mem+swap hits the limit, trying to swapout pages is meaningless > > as it doesn't change mem+swap usage. > > > Good catch...sigh, I missed this disussion. > > > > > What do you think of this patch? > > === > > From: Daisuke Nishimura > > > > vmscan-rename-scmay_swap-to-may_unmap.patch removed may_swap flag, > > but memcg had used it as a flag for "we need to use swap?", as the > > name indicate. > > > > And in current implementation, memcg cannot reclaim mapped file caches > > when mem+swap hits the limit. > > > When mem+swap hits the limit, swap-out anonymous page doesn't reduce the > amount of usage of mem+swap, so, swap-out should be avoided. > > > re-introduce may_swap flag and handle it at shrink_page_list. > > > > This patch doesn't influence any scan_control users other than memcg. > > > > > > Signed-off-by: Daisuke Nishimura > > Seems good, > Reviewed-by: KAMEZAWA Hiroyuki > > But hum....Maybe this lru scan work in the same way as the case > of !total_swap_pages. (means don't scan anon LRU.) > revisit this later. Well, How about following patch? So, I have to agree my judgement of may_unmap was wrong. You explain memcg can use may_swap instead may_unmap. and I think other may_unmap user (zone_reclaim and shrink_all_list) can convert may_unmap code to may_swap. IOW, Nishimura-san, you explain we can remove the branch of the may_unmap from shrink_page_list(). it's really good job. thanks! ======== Subject: vmswan: reintroduce sc->may_swap vmscan-rename-scmay_swap-to-may_unmap.patch removed may_swap flag, but memcg had used it as a flag for "we need to use swap?", as the name indicate. And in current implementation, memcg cannot reclaim mapped file caches when mem+swap hits the limit. re-introduce may_swap flag and handle it at get_scan_ratio(). This patch doesn't influence any scan_control users other than memcg. Signed-off-by: KOSAKI Motohiro Signed-off-by: Daisuke Nishimura -- mm/vmscan.c | 12 ++++++++++-- 1 files changed, 10 insertions(+), 2 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 3be6157..00ea4a1 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -63,6 +63,9 @@ struct scan_control { /* Can mapped pages be reclaimed? */ int may_unmap; + /* Can pages be swapped as part of reclaim? */ + int may_swap; + /* This context's SWAP_CLUSTER_MAX. If freeing memory for * suspend, we effectively ignore SWAP_CLUSTER_MAX. * In this context, it doesn't matter that we scan the @@ -1379,7 +1382,7 @@ static void get_scan_ratio(struct zone *zone, struct scan_control *sc, struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); /* If we have no swap space, do not bother scanning anon pages. */ - if (nr_swap_pages <= 0) { + if (!sc->may_swap || (nr_swap_pages <= 0)) { percent[0] = 0; percent[1] = 100; return; @@ -1695,6 +1698,7 @@ unsigned long try_to_free_pages(struct zonelist *zonelist, int order, .may_writepage = !laptop_mode, .swap_cluster_max = SWAP_CLUSTER_MAX, .may_unmap = 1, + .may_swap = 1, .swappiness = vm_swappiness, .order = order, .mem_cgroup = NULL, @@ -1714,6 +1718,7 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont, struct scan_control sc = { .may_writepage = !laptop_mode, .may_unmap = 1, + .may_swap = 1, .swap_cluster_max = SWAP_CLUSTER_MAX, .swappiness = swappiness, .order = 0, @@ -1723,7 +1728,7 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont, struct zonelist *zonelist; if (noswap) - sc.may_unmap = 0; + sc.may_swap = 0; sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); @@ -1763,6 +1768,7 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order) struct scan_control sc = { .gfp_mask = GFP_KERNEL, .may_unmap = 1, + .may_swap = 1, .swap_cluster_max = SWAP_CLUSTER_MAX, .swappiness = vm_swappiness, .order = order, @@ -2109,6 +2115,7 @@ unsigned long shrink_all_memory(unsigned long nr_pages) struct scan_control sc = { .gfp_mask = GFP_KERNEL, .may_unmap = 0, + .may_swap = 1, .swap_cluster_max = nr_pages, .may_writepage = 1, .isolate_pages = isolate_pages_global, @@ -2289,6 +2296,7 @@ static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) struct scan_control sc = { .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE), .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP), + .may_swap = 1, .swap_cluster_max = max_t(unsigned long, nr_pages, SWAP_CLUSTER_MAX), .gfp_mask = gfp_mask, -- 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/