From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f70.google.com (mail-pg0-f70.google.com [74.125.83.70]) by kanga.kvack.org (Postfix) with ESMTP id C4FF96B0038 for ; Fri, 3 Feb 2017 01:17:40 -0500 (EST) Received: by mail-pg0-f70.google.com with SMTP id 204so12404966pge.5 for ; Thu, 02 Feb 2017 22:17:40 -0800 (PST) Received: from lgeamrelo11.lge.com (LGEAMRELO11.lge.com. [156.147.23.51]) by mx.google.com with ESMTP id 33si24576334plg.204.2017.02.02.22.17.38 for ; Thu, 02 Feb 2017 22:17:39 -0800 (PST) Date: Fri, 3 Feb 2017 15:17:37 +0900 From: Minchan Kim Subject: Re: [PATCH 1/2 v3] mm: vmscan: do not pass reclaimed slab to vmpressure Message-ID: <20170203061737.GA32372@bbox> References: <1485504817-3124-1-git-send-email-vinmenon@codeaurora.org> <1485853328-7672-1-git-send-email-vinmenon@codeaurora.org> <20170202104422.GF22806@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170202104422.GF22806@dhcp22.suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Vinayak Menon , akpm@linux-foundation.org, hannes@cmpxchg.org, mgorman@techsingularity.net, vbabka@suse.cz, riel@redhat.com, vdavydov.dev@gmail.com, anton.vorontsov@linaro.org, shashim@codeaurora.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org On Thu, Feb 02, 2017 at 11:44:22AM +0100, Michal Hocko wrote: > On Tue 31-01-17 14:32:08, Vinayak Menon wrote: > > During global reclaim, the nr_reclaimed passed to vmpressure > > includes the pages reclaimed from slab. But the corresponding > > scanned slab pages is not passed. This can cause total reclaimed > > pages to be greater than scanned, causing an unsigned underflow > > in vmpressure resulting in a critical event being sent to root > > cgroup. So do not consider reclaimed slab pages for vmpressure > > calculation. The reclaimed pages from slab can be excluded because > > the freeing of a page by slab shrinking depends on each slab's > > object population, making the cost model (i.e. scan:free) different > > from that of LRU. > > This might be true but what happens if the slab reclaim contributes > significantly to the overal reclaim? This would be quite rare but not > impossible. Of course, it is better for vmpressure to cover slab but it's not easy without page-based shrinking model, I think. It wold make vmpressure higher easily due to low reclaim efficiency compared to LRU pages. Yeah, vmpressure is not a perfect but no need to add more noises, either. It's regression since 6b4f7799c6a5 so I think this patch should go first and if someone want to cover slab really, he should spend a time to work it well. It's too much that Vinayak shuld make a effort for that. -- 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