From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f199.google.com (mail-pf0-f199.google.com [209.85.192.199]) by kanga.kvack.org (Postfix) with ESMTP id 22915280947 for ; Sat, 11 Mar 2017 12:52:18 -0500 (EST) Received: by mail-pf0-f199.google.com with SMTP id l66so221561075pfl.6 for ; Sat, 11 Mar 2017 09:52:18 -0800 (PST) Received: from mail-pg0-x233.google.com (mail-pg0-x233.google.com. [2607:f8b0:400e:c05::233]) by mx.google.com with ESMTPS id s196si6757364pfs.153.2017.03.11.09.52.17 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 11 Mar 2017 09:52:17 -0800 (PST) Received: by mail-pg0-x233.google.com with SMTP id 25so49812332pgy.0 for ; Sat, 11 Mar 2017 09:52:17 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <1489240264-3290-1-git-send-email-ysxie@foxmail.com> References: <1489240264-3290-1-git-send-email-ysxie@foxmail.com> From: Shakeel Butt Date: Sat, 11 Mar 2017 09:52:15 -0800 Message-ID: Subject: Re: [PATCH v2 RFC] mm/vmscan: more restrictive condition for retry in do_try_to_free_pages Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Yisheng Xie Cc: Andrew Morton , Johannes Weiner , Mel Gorman , Vlastimil Babka , Michal Hocko , riel@redhat.com, Linux MM , LKML , xieyisheng1@huawei.com, guohanjun@huawei.com, Xishi Qiu On Sat, Mar 11, 2017 at 5:51 AM, Yisheng Xie wrote: > From: Yisheng Xie > > When we enter do_try_to_free_pages, the may_thrash is always clear, and > it will retry shrink zones to tap cgroup's reserves memory by setting > may_thrash when the former shrink_zones reclaim nothing. > > However, when memcg is disabled or on legacy hierarchy, it should not do > this useless retry at all, for we do not have any cgroup's reserves > memory to tap, and we have already done hard work but made no progress. > > To avoid this time costly and useless retrying, add a stub function > may_thrash and return true when memcg is disabled or on legacy > hierarchy. > > Signed-off-by: Yisheng Xie > Suggested-by: Shakeel Butt > --- > v2: > - more restrictive condition for retry of shrink_zones (restricting > cgroup_disabled=memory boot option and cgroup legacy hierarchy) - Shakeel > > - add a stub function may_thrash() to avoid compile error or warning. > > - rename subject from "donot retry shrink zones when memcg is disable" > to "more restrictive condition for retry in do_try_to_free_pages" > > Any comment is more than welcome! > > Thanks > Yisheng Xie > > mm/vmscan.c | 20 +++++++++++++++++++- > 1 file changed, 19 insertions(+), 1 deletion(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index bc8031e..415f800 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -184,6 +184,19 @@ static bool sane_reclaim(struct scan_control *sc) > #endif > return false; > } > + > +static bool may_thrash(struct scan_control *sc) > +{ > + /* > + * When memcg is disabled or on legacy hierarchy, there is no cgroup > + * reserves memory to tap. > + */ > + if (!cgroup_subsys_enabled(memory_cgrp_subsys) || > + !cgroup_subsys_on_dfl(memory_cgrp_subsys)) > + return true; > + > + return sc->may_thrash; > +} > #else > static bool global_reclaim(struct scan_control *sc) > { > @@ -194,6 +207,11 @@ static bool sane_reclaim(struct scan_control *sc) > { > return true; > } > + > +static bool may_thrash(struct scan_control *sc) > +{ > + return true; > +} > #endif > > /* > @@ -2808,7 +2826,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist, > return 1; > > /* Untapped cgroup reserves? Don't OOM, retry. */ > - if (!sc->may_thrash) { > + if (!may_thrash(sc)) { Thanks Yisheng. The name of the function may_thrash() is confusing in the sense that it is returning exactly the opposite of what its name implies. How about reversing the condition of may_thrash() function and change the scan_control's field may_thrash to thrashed? > sc->priority = initial_priority; > sc->may_thrash = 1; > goto retry; > -- > 1.9.1 > -- 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