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[109.81.21.195]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-43b4389321csm12045529f8f.29.2026.03.16.13.02.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 16 Mar 2026 13:02:39 -0700 (PDT) Date: Mon, 16 Mar 2026 21:02:38 +0100 From: Michal Hocko To: "zhaoyang.huang" Cc: Andrew Morton , Yu Zhao , Rik van Riel , Shakeel Butt , Roman Gushchin , Johannes Weiner , "T . J . Mercier" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Zhaoyang Huang , steve.kang@unisoc.com Subject: Re: [PATCH] mm: remove '!root_reclaim' checking in should_abort_scan() Message-ID: References: <20260212032111.408865-1-zhaoyang.huang@unisoc.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260212032111.408865-1-zhaoyang.huang@unisoc.com> On Thu 12-02-26 11:21:11, zhaoyang.huang wrote: > From: Zhaoyang Huang > > Nowadays, ANDROID system replaces madivse with memory.reclaim to implement > user space memory management which desires to reclaim a certain amount of > memcg's memory. However, oversized reclaiming and high latency are observed > as there is no limitation over nr_reclaimed inside try_to_shrink_lruvec > when MGLRU enabled. Besides, this could also affect all none root_reclaim > such as reclaim_high etc. > Since the commit 'b82b530740b9' ("mm: vmscan: restore incremental cgroup > iteration") introduces sc->memcg_full_walk to limit the walk range of > mem_cgroup_iter and keep the fairness among the descendants of one memcg. > This commit would like to make single memcg's scanning more precised by > removing the criteria of 'if (!root_reclaim)' inside > should_abort_scan(). This changelog, similar to its previous version is lacking details on what exactly is going on. How much over-reclaim are we talking about here? Is this MGLRU specific? Why doesn't our standard over-reclaim protection work? > Suggested-by: T.J.Mercier > Signed-off-by: Zhaoyang Huang > --- > mm/vmscan.c | 4 ---- > 1 file changed, 4 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 670fe9fae5ba..9d900be478ea 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -4832,10 +4832,6 @@ static bool should_abort_scan(struct lruvec *lruvec, struct scan_control *sc) > int i; > enum zone_watermarks mark; > > - /* don't abort memcg reclaim to ensure fairness */ > - if (!root_reclaim(sc)) > - return false; > - > if (sc->nr_reclaimed >= max(sc->nr_to_reclaim, compact_gap(sc->order))) > return true; > > -- > 2.25.1 > -- Michal Hocko SUSE Labs