From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D0435C43381 for ; Wed, 6 Jan 2021 17:40:50 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 6A8F420657 for ; Wed, 6 Jan 2021 17:40:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6A8F420657 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id A1B386B02B5; Wed, 6 Jan 2021 12:40:46 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 816D96B02B8; Wed, 6 Jan 2021 12:40:46 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6678C6B02B6; Wed, 6 Jan 2021 12:40:46 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0136.hostedemail.com [216.40.44.136]) by kanga.kvack.org (Postfix) with ESMTP id 37CDD6B02B7 for ; Wed, 6 Jan 2021 12:40:46 -0500 (EST) Received: from smtpin03.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 9F12B3624 for ; Wed, 6 Jan 2021 17:40:45 +0000 (UTC) X-FDA: 77676065250.03.plot13_6311029274e3 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin03.hostedemail.com (Postfix) with ESMTP id 7E73D28A4E9 for ; Wed, 6 Jan 2021 17:40:45 +0000 (UTC) X-HE-Tag: plot13_6311029274e3 X-Filterd-Recvd-Size: 2369 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf24.hostedemail.com (Postfix) with ESMTP for ; Wed, 6 Jan 2021 17:40:44 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 92CD9AD64; Wed, 6 Jan 2021 17:40:43 +0000 (UTC) From: Vlastimil Babka To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Vladimir Davydov , Qian Cai , David Hildenbrand , Michal Hocko , Vlastimil Babka Subject: [RFC 0/3] mm, slab, slub: remove cpu and memory hotplug locks Date: Wed, 6 Jan 2021 18:40:26 +0100 Message-Id: <20210106174029.12654-1-vbabka@suse.cz> X-Mailer: git-send-email 2.29.2 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable 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: Hi, some related work caused me to look at how we use get/put_mems_online() a= nd get/put_online_cpus() during kmem cache creation/descruction/shrinking, a= nd realize that it should be actually safe to remove all of that with rather= small effort (as e.g. Michal Hocko suspected in some of the past discussions already). This has the benefit to avoid rather heavy locks that have caus= ed locking order issues already in the past. So this is the result, Patches = 1 and 2 remove memory hotplug and cpu hotplug locking, respectively. Patch 3 is= due to realization that in fact some races exist despite the locks (even if n= ot removed), but the most sane solution is not to introduce more of them, bu= t rather accept some wasted memory in scenarios that should be rare anyway = (full memory hot remove), as we do the same in other contexts already. It's all= RFC for now, as I might have missed some reason why it's not safe. Vlastimil Babka (3): mm, slab, slub: stop taking memory hotplug lock mm, slab, slub: stop taking cpu hotplug lock mm, slub: stop freeing kmem_cache_node structures on node offline mm/slab_common.c | 20 ++++-------------- mm/slub.c | 54 ++++++++++++++++++++++++++++++++---------------- 2 files changed, 40 insertions(+), 34 deletions(-) --=20 2.29.2