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Mon, 03 Aug 2020 11:27:00 -0400 X-MC-Unique: XNnLbSbkPuekjlT3O8r6aw-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 0CE328017FB; Mon, 3 Aug 2020 15:26:59 +0000 (UTC) Received: from colo-mx.corp.redhat.com (colo-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.21]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E11DB87E36; Mon, 3 Aug 2020 15:26:58 +0000 (UTC) Received: from zmail18.collab.prod.int.phx2.redhat.com (zmail18.collab.prod.int.phx2.redhat.com [10.5.83.21]) by colo-mx.corp.redhat.com (Postfix) with ESMTP id 8D3029A0EE; Mon, 3 Aug 2020 15:26:58 +0000 (UTC) Date: Mon, 3 Aug 2020 11:26:56 -0400 (EDT) From: Waiman Long Reply-To: Waiman Long To: Yafang Shao Cc: Michal Hocko , Johannes Weiner , Andrew Morton , Linux MM Message-ID: <1448744273.26026905.1596468416644.JavaMail.zimbra@redhat.com> In-Reply-To: References: <20200728074032.1555-1-laoar.shao@gmail.com> <20200730112620.GH18727@dhcp22.suse.cz> <20200803101226.GH5174@dhcp22.suse.cz> <20200803135636.GN5174@dhcp22.suse.cz> Subject: Re: [PATCH] mm, memcg: do full scan initially in force_empty MIME-Version: 1.0 X-Originating-IP: [10.10.117.107, 10.4.195.9] Thread-Topic: mm, memcg: do full scan initially in force_empty Thread-Index: HBc5K/Oqthnb3n+iyjgsb7nvXxyGkw== X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 25EA337609 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam02 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: Yafang, >> >> > The force_empty will also drop the pagecache pages, which is not >> > expected by us. >> >> force_empty is intended to reclaim _all_ pages. >> >> > The global drop_caches can't work either because it will drop slabs in >> > other memcgs. >> > That is why I want to introduce per memcg drop_caches. >> >> Problems with negative dentries has been already discussed in the past. >> I believe there was no conclusion so far. Please try to dig into >> archives. > >I have read the proposal of Waiman. But it seems there isn't a conclusion yet. >If the kernel can't fix this issue perfectly, then giving the user a >chance to work around it would be a possible solution - drop_caches is >that kind of workaround. I am sorry for failing to follow up on the negative dentry patches. Is your reason of doing this patch primarily because of the negative dentry build-up? Uncontrollable negative dentry buildup is a problem that should be addressed. I will work on an updated patch and post it ASAP. Cheers, Longman