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 340C8C433E0 for ; Wed, 13 Jan 2021 13:17:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DD41D23432 for ; Wed, 13 Jan 2021 13:17:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726735AbhAMNR2 (ORCPT ); Wed, 13 Jan 2021 08:17:28 -0500 Received: from mx2.suse.de ([195.135.220.15]:56768 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726594AbhAMNR1 (ORCPT ); Wed, 13 Jan 2021 08:17:27 -0500 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 61F64B7D4; Wed, 13 Jan 2021 13:16:46 +0000 (UTC) From: Vlastimil Babka To: Andrew Morton , 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: [PATCH 0/3] mm, slab, slub: remove cpu and memory hotplug locks Date: Wed, 13 Jan 2021 14:16:31 +0100 Message-Id: <20210113131634.3671-1-vbabka@suse.cz> X-Mailer: git-send-email 2.29.2 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Changes since RFC: - lockdep didn't like reintroducing slab_mutex in kmem_cache_shrink(), so instead explain why it's not needed after all (in Patch 2) - the above is only safe with Patch 1 already in place, so order it first (current Patch 1 was Patch 3 in RFC) Some related work caused me to look at how we use get/put_mems_online() and get/put_online_cpus() during kmem cache creation/descruction/shrinking, and 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 caused locking order issues already in the past. So this is the result, Patches 2 and 3 remove memory hotplug and cpu hotplug locking, respectively. Patch 1 is due to realization that in fact some races exist despite the locks (even if not removed), but the most sane solution is not to introduce more of them, but 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. Vlastimil Babka (3): mm, slub: stop freeing kmem_cache_node structures on node offline mm, slab, slub: stop taking memory hotplug lock mm, slab, slub: stop taking cpu hotplug lock mm/slab_common.c | 18 ++-------------- mm/slub.c | 56 +++++++++++++++++++++++++++++++----------------- 2 files changed, 38 insertions(+), 36 deletions(-) -- 2.29.2