From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx129.postini.com [74.125.245.129]) by kanga.kvack.org (Postfix) with SMTP id C1A226B13F6 for ; Mon, 6 Feb 2012 19:22:43 -0500 (EST) Received: from m2.gw.fujitsu.co.jp (unknown [10.0.50.72]) by fgwmail6.fujitsu.co.jp (Postfix) with ESMTP id ECD2E3EE0AE for ; Tue, 7 Feb 2012 09:22:41 +0900 (JST) Received: from smail (m2 [127.0.0.1]) by outgoing.m2.gw.fujitsu.co.jp (Postfix) with ESMTP id D51BC45DE61 for ; Tue, 7 Feb 2012 09:22:41 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (s2.gw.fujitsu.co.jp [10.0.50.92]) by m2.gw.fujitsu.co.jp (Postfix) with ESMTP id B435645DD74 for ; Tue, 7 Feb 2012 09:22:41 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id A74AE1DB803A for ; Tue, 7 Feb 2012 09:22:41 +0900 (JST) Received: from m107.s.css.fujitsu.com (m107.s.css.fujitsu.com [10.240.81.147]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id 538BC1DB802C for ; Tue, 7 Feb 2012 09:22:41 +0900 (JST) Date: Tue, 7 Feb 2012 09:21:20 +0900 From: KAMEZAWA Hiroyuki Subject: Re: [PATCH] memcg: fix up documentation on global LRU. Message-Id: <20120207092120.c79d8b73.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: References: <1328233033-14246-1-git-send-email-yinghan@google.com> <20120203161140.GC13461@tiehlicka.suse.cz> <20120206104649.01a89d66.kamezawa.hiroyu@jp.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Ying Han Cc: Michal Hocko , Balbir Singh , Rik van Riel , Hugh Dickins , Johannes Weiner , Mel Gorman , Pavel Emelyanov , linux-mm@kvack.org On Mon, 6 Feb 2012 12:00:49 -0800 Ying Han wrote: > On Sun, Feb 5, 2012 at 5:46 PM, KAMEZAWA Hiroyuki > wrote: > > On Fri, 3 Feb 2012 12:15:59 -0800 > > Ying Han wrote: > > > >> On Fri, Feb 3, 2012 at 8:11 AM, Michal Hocko wrote: > >> > On Thu 02-02-12 17:37:13, Ying Han wrote: > >> >> In v3.3-rc1, the global LRU has been removed with commit > >> >> "mm: make per-memcg LRU lists exclusive". The patch fixes up the memcg docs. > >> >> > >> >> Signed-off-by: Ying Han > >> > > >> > For the global LRU removal > >> > Acked-by: Michal Hocko > >> > > >> > see the comment about the swap extension bellow. > >> > > >> > Thanks > >> > > >> >> --- > >> >> A Documentation/cgroups/memory.txt | A 25 ++++++++++++------------- > >> >> A 1 files changed, 12 insertions(+), 13 deletions(-) > >> >> > >> >> diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt > >> >> index 4c95c00..847a2a4 100644 > >> >> --- a/Documentation/cgroups/memory.txt > >> >> +++ b/Documentation/cgroups/memory.txt > >> > [...] > >> >> @@ -209,19 +208,19 @@ In this case, setting memsw.limit_in_bytes=3G will prevent bad use of swap. > >> >> A By using memsw limit, you can avoid system OOM which can be caused by swap > >> >> A shortage. > >> >> > >> >> -* why 'memory+swap' rather than swap. > >> >> -The global LRU(kswapd) can swap out arbitrary pages. Swap-out means > >> >> -to move account from memory to swap...there is no change in usage of > >> >> -memory+swap. In other words, when we want to limit the usage of swap without > >> >> -affecting global LRU, memory+swap limit is better than just limiting swap from > >> >> -OS point of view. > >> >> - > >> >> A * What happens when a cgroup hits memory.memsw.limit_in_bytes > >> >> A When a cgroup hits memory.memsw.limit_in_bytes, it's useless to do swap-out > >> >> A in this cgroup. Then, swap-out will not be done by cgroup routine and file > >> >> -caches are dropped. But as mentioned above, global LRU can do swapout memory > >> >> -from it for sanity of the system's memory management state. You can't forbid > >> >> -it by cgroup. > >> >> +caches are dropped. > >> >> + > >> >> +TODO: > >> >> +* use 'memory+swap' rather than swap was due to existence of global LRU. > >> > >> I wasn't sure about the initial comment while making the patch. Since > >> it mentions something about global LRU, which i figured we need to > >> revisit it anyway. > >> > > > > The "global LRU" here means 'the health of the whole memory management". > > memory+swap guarantees memcg will never be obstacles for routines which > > works for system memory management. > > > > soft-limit _is_ a hint for global lru. but memory+swap will never be. > > > Thank you for the clarification. So the "global LRU" should be > interpreted as global pressure, i guess? You're right. > I can imagine some extra complexities on two limit (in memory & swap) vs one limit > (memory+swap). > > I will go ahead post the first patch and leave the swap change behind. > Apparently I don't know the initial design much, and feel free to post > the second half. > Ok, I'll check. Thanks, -Kame -- 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/ . 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