From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx142.postini.com [74.125.245.142]) by kanga.kvack.org (Postfix) with SMTP id 02ADE6B13F1 for ; Mon, 6 Feb 2012 15:00:50 -0500 (EST) Received: by qadz32 with SMTP id z32so2554273qad.14 for ; Mon, 06 Feb 2012 12:00:50 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <20120206104649.01a89d66.kamezawa.hiroyu@jp.fujitsu.com> References: <1328233033-14246-1-git-send-email-yinghan@google.com> <20120203161140.GC13461@tiehlicka.suse.cz> <20120206104649.01a89d66.kamezawa.hiroyu@jp.fujitsu.com> Date: Mon, 6 Feb 2012 12:00:49 -0800 Message-ID: Subject: Re: [PATCH] memcg: fix up documentation on global LRU. From: Ying Han Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: KAMEZAWA Hiroyuki Cc: Michal Hocko , Balbir Singh , Rik van Riel , Hugh Dickins , Johannes Weiner , Mel Gorman , Pavel Emelyanov , linux-mm@kvack.org 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 memc= g docs. >> >> >> >> Signed-off-by: Ying Han >> > >> > For the global LRU removal >> > Acked-by: Michal Hocko >> > >> > see the comment about the swap extension bellow. >> > >> > Thanks >> > >> >> --- >> >> =A0Documentation/cgroups/memory.txt | =A0 25 ++++++++++++------------= - >> >> =A01 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=3D3G= will prevent bad use of swap. >> >> =A0By using memsw limit, you can avoid system OOM which can be caused= by swap >> >> =A0shortage. >> >> >> >> -* 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. >> >> - >> >> =A0* What happens when a cgroup hits memory.memsw.limit_in_bytes >> >> =A0When a cgroup hits memory.memsw.limit_in_bytes, it's useless to do= swap-out >> >> =A0in 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 swapou= t 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? 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. --Ying > > 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org