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[98.15.154.102]) by smtp.gmail.com with ESMTPSA id z186sm14056056qke.59.2021.09.21.07.28.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 21 Sep 2021 07:28:20 -0700 (PDT) Date: Tue, 21 Sep 2021 10:30:21 -0400 From: Johannes Weiner To: Yongmei Xie Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm:vmscan remove unnecessary lru lock unlock/lock pair Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=cmpxchg-org.20210112.gappssmtp.com header.s=20210112 header.b=8PcY0Jw2; spf=pass (imf29.hostedemail.com: domain of hannes@cmpxchg.org designates 209.85.222.169 as permitted sender) smtp.mailfrom=hannes@cmpxchg.org; dmarc=pass (policy=none) header.from=cmpxchg.org X-Stat-Signature: nqq36mm1aracgyddug6m61kg3h3ta7oo X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 0E1E99000263 X-HE-Tag: 1632234501-97573 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: Hello Yongmei, On Sun, Sep 19, 2021 at 11:24:30PM +0800, Yongmei Xie wrote: > There's code redundant in move_pages_to_lru. When there're multiple of mlocked pages > or compound pages, the original implementation tries to unlock and then lock to handle > some exceptional case. > > Signed-off-by: Yongmei Xie > --- > mm/vmscan.c | 32 ++++++++++++++++++++++++-------- > 1 file changed, 24 insertions(+), 8 deletions(-) Is the lock cycling creating actual problems for you? The locks aren't batched because we expect those situations to be rare: mlock or truncate/munmap racing with reclaim isolation. And in fact, you're adding an unconditional lock cycle and more branches to the hot path to deal with it. It's more code overall. Without data, the patch isn't very compelling. If you do have data, it would be good to include it in the changelog. Thanks!