From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f72.google.com (mail-ed1-f72.google.com [209.85.208.72]) by kanga.kvack.org (Postfix) with ESMTP id 5FFFB6B68EB for ; Mon, 3 Dec 2018 06:56:48 -0500 (EST) Received: by mail-ed1-f72.google.com with SMTP id c53so6482390edc.9 for ; Mon, 03 Dec 2018 03:56:48 -0800 (PST) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id l11-v6si3021232ejz.109.2018.12.03.03.56.46 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 03 Dec 2018 03:56:47 -0800 (PST) Date: Mon, 3 Dec 2018 12:56:46 +0100 From: Michal Hocko Subject: Re: [PATCH 2/3] mm/vmscan: Enable kswapd to reclaim low-protected memory Message-ID: <20181203115646.GP31738@dhcp22.suse.cz> References: <20181203080119.18989-1-xlpang@linux.alibaba.com> <20181203080119.18989-2-xlpang@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181203080119.18989-2-xlpang@linux.alibaba.com> Sender: owner-linux-mm@kvack.org List-ID: To: Xunlei Pang Cc: Roman Gushchin , Johannes Weiner , linux-kernel@vger.kernel.org, linux-mm@kvack.org On Mon 03-12-18 16:01:18, Xunlei Pang wrote: > There may be cgroup memory overcommitment, it will become > even common in the future. > > Let's enable kswapd to reclaim low-protected memory in case > of memory pressure, to mitigate the global direct reclaim > pressures which could cause jitters to the response time of > lantency-sensitive groups. Please be more descriptive about the problem you are trying to handle here. I haven't actually read the patch but let me emphasise that the low limit protection is important isolation tool. And allowing kswapd to reclaim protected memcgs is going to break the semantic as it has been introduced and designed. > > Signed-off-by: Xunlei Pang > --- > mm/vmscan.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 62ac0c488624..3d412eb91f73 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -3531,6 +3531,7 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx) > > count_vm_event(PAGEOUTRUN); > > +retry: > do { > unsigned long nr_reclaimed = sc.nr_reclaimed; > bool raise_priority = true; > @@ -3622,6 +3623,13 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx) > sc.priority--; > } while (sc.priority >= 1); > > + if (!sc.nr_reclaimed && sc.memcg_low_skipped) { > + sc.priority = DEF_PRIORITY; > + sc.memcg_low_reclaim = 1; > + sc.memcg_low_skipped = 0; > + goto retry; > + } > + > if (!sc.nr_reclaimed) > pgdat->kswapd_failures++; > > -- > 2.13.5 (Apple Git-94) > -- Michal Hocko SUSE Labs