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[195.135.220.15]) by mx.google.com with ESMTPS id b57si2285636edd.393.2019.06.10.14.37.01 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 10 Jun 2019 14:37:02 -0700 (PDT) Received-SPF: pass (google.com: domain of osalvador@suse.de designates 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=pass (google.com: domain of osalvador@suse.de designates 195.135.220.15 as permitted sender) smtp.mailfrom=osalvador@suse.de X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 720E7AAA8; Mon, 10 Jun 2019 21:37:00 +0000 (UTC) Message-ID: <1560202615.3312.6.camel@suse.de> Subject: Re: [v7 PATCH 1/2] mm: vmscan: remove double slab pressure by inc'ing sc->nr_scanned From: Oscar Salvador To: Yang Shi , ying.huang@intel.com, hannes@cmpxchg.org, mhocko@suse.com, mgorman@techsingularity.net, kirill.shutemov@linux.intel.com, josef@toxicpanda.com, hughd@google.com, shakeelb@google.com, hdanton@sina.com, akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org Date: Mon, 10 Jun 2019 23:36:55 +0200 In-Reply-To: <1559025859-72759-1-git-send-email-yang.shi@linux.alibaba.com> References: <1559025859-72759-1-git-send-email-yang.shi@linux.alibaba.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.26.1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, 2019-05-28 at 14:44 +0800, Yang Shi wrote: > The commit 9092c71bb724 ("mm: use sc->priority for slab shrink > targets") > has broken up the relationship between sc->nr_scanned and slab > pressure. > The sc->nr_scanned can't double slab pressure anymore. So, it sounds > no > sense to still keep sc->nr_scanned inc'ed. Actually, it would > prevent > from adding pressure on slab shrink since excessive sc->nr_scanned > would > prevent from scan->priority raise. Hi Yang, I might be misunderstanding this, but did you mean "prevent from scan- priority decreasing"? I guess we are talking about balance_pgdat(), and in case kswapd_shrink_node() returns true (it means we have scanned more than we had to reclaim), raise_priority becomes false, and this does not let sc->priority to be decreased, which has the impact that less pages will be reclaimed the next round. Sorry for bugging here, I just wanted to see if I got this right. -- Oscar Salvador SUSE L3