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Sat, 12 Nov 2022 06:23:38 -0800 (PST) Date: Sat, 12 Nov 2022 09:23:41 -0500 From: Johannes Weiner To: Hongchen Zhang Cc: Andrew Morton , Mel Gorman , Hugh Dickins , Joonsoo Kim , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, Yosry Ahmed Subject: Re: [PATCH] mm: vmscan: fix extreme overreclaim and swap floods Message-ID: References: <20220802162811.39216-1-hannes@cmpxchg.org> <17f04d65-020e-a52d-41e8-0d540e32b475@loongson.cn> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <17f04d65-020e-a52d-41e8-0d540e32b475@loongson.cn> ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1668263021; a=rsa-sha256; cv=none; b=RentzhTkdmCC9t5F6igmpw+fIjZY5QKK/JgxF6r7Ue8XVuV1xWwcGXIbB7PATImK5La52i 2cQu5aGu12jcHXD9xTWwMOcq+Z4NfM8I7AcQLWu3my4miXJJ5aTQC2RAQS9YDtCrCtDeY/ Mzzyu8zsmb1TPMJziOr76A2KIuQCut0= ARC-Authentication-Results: i=1; imf20.hostedemail.com; dkim=pass header.d=cmpxchg-org.20210112.gappssmtp.com header.s=20210112 header.b=w+EQNfOU; 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dmarc=pass (policy=none) header.from=cmpxchg.org X-Rspamd-Server: rspam10 X-Rspam-User: X-Rspamd-Queue-Id: 9D6801C0004 X-HE-Tag: 1668263020-187260 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, Sep 20, 2022 at 02:12:17PM +0800, Hongchen Zhang wrote: > On 2022/8/3 am 12:28, Johannes Weiner wrote: > > @@ -2988,8 +2988,6 @@ static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc) > > nr_scanned = targets[lru] - nr[lru]; > > nr[lru] = targets[lru] * (100 - percentage) / 100; > > nr[lru] -= min(nr[lru], nr_scanned); > We should not just remove the following line because kswapd may also call > this function and there is no side effect to do scan adjust for kswapd,so it > may be better to change like this: > + if (current_is_kswapd()) > scan_adjusted = true; > > - > > - scan_adjusted = true There is no scan_adjusted after this patch. If you're saying that kswapd should set proportional_reclaim unconditionally, then no, it should not. Proportional reclaim is not safe at lower priority levels, as the changelog outlines in detail.