From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with ESMTP id E7FA86B004A for ; Thu, 30 Jun 2011 21:06:43 -0400 (EDT) Date: Thu, 30 Jun 2011 18:06:53 -0700 From: Andrew Morton Subject: Re: [PATCH] [Cleanup] memcg: export memory cgroup's swappiness v2 Message-Id: <20110630180653.1df10f38.akpm@linux-foundation.org> In-Reply-To: <20110701092059.be4400f7.kamezawa.hiroyu@jp.fujitsu.com> References: <20110629190325.28aa2dc6.kamezawa.hiroyu@jp.fujitsu.com> <20110630130134.63a1dd37.akpm@linux-foundation.org> <20110701085013.4e8cbb02.kamezawa.hiroyu@jp.fujitsu.com> <20110701092059.be4400f7.kamezawa.hiroyu@jp.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: KAMEZAWA Hiroyuki Cc: "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "nishimura@mxp.nes.nec.co.jp" , "bsingharora@gmail.com" , Michal Hocko , Ying Han , Shaohua Li , KOSAKI Motohiro On Fri, 1 Jul 2011 09:20:59 +0900 KAMEZAWA Hiroyuki wrote: > On Fri, 1 Jul 2011 08:50:13 +0900 > KAMEZAWA Hiroyuki wrote: > > > On Thu, 30 Jun 2011 13:01:34 -0700 > > Andrew Morton wrote: > > > Ok, I'll check it. Maybe I miss !CONFIG_SWAP... > > > > v4 here. Thank you for pointing out. I could think of several ways but > maybe this one is good because using vm_swappines with !CONFIG_SWAP seems > to be a bug. No, it isn't a bug - swappiness also controls the kernel's eagerness to unmap and reclaim mmapped pagecache. > tested with allyesconfig/allnoconfig. Did it break the above? > +#ifdef CONFIG_SWAP > +static int vmscan_swappiness(struct scan_control *sc) > +{ > + if (scanning_global_lru(sc)) > + return vm_swappiness; Well that's a bit ugly - it assumes that all callers set scan_control.swappiness to vm_swappiness then never change it. That may be true in the current code. Ho hum, I guess that's a simplification we can make. > + return mem_cgroup_swappiness(sc->mem_cgroup); > +} > +#else > +static int vmscan_swappiness(struct scan_control *sc) > +{ > + /* Now, this function is never called with !CONFIG_SWAP */ > + BUG(); > + return 0; > +} > +#endif > > ... > > @@ -1789,8 +1804,8 @@ static void get_scan_count(struct zone *zone, struct scan_control *sc, > * With swappiness at 100, anonymous and file have the same priority. > * This scanning priority is essentially the inverse of IO cost. > */ > - anon_prio = sc->swappiness; > - file_prio = 200 - sc->swappiness; > + anon_prio = vmscan_swappiness(sc); > + file_prio = 200 - vmscan_swappiness(sc); hah, this should go BUG if CONFIG_SWAP=n. But it won't, because we broke get_scan_count(). It fails to apply vm_swappiness to file-backed pages if there's no available swap, which is daft. I think this happened in 76a33fc380c9a ("vmscan: prevent get_scan_ratio() rounding errors") which claims "this patch doesn't really change logics, but just increase precision". -- 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