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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BEF1AC433F5 for ; Wed, 18 May 2022 18:01:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241251AbiERSAz (ORCPT ); Wed, 18 May 2022 14:00:55 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44228 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231206AbiERSAw (ORCPT ); Wed, 18 May 2022 14:00:52 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 4F709344F3 for ; Wed, 18 May 2022 11:00:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1652896848; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=uRSjnnvJryZVWYf6M7LCjtH2BWC65H+7nO7Y0CFrMDg=; b=RBCjTQNsSVdM43ZqmneBENDB95UPtS20Xz0WLmflAtWiVCxY1j+418omB6xfnkGCmsd0P+ /YPPPJUM2E0JbjP3A8VMeEs4XGC30ZQsEdeYwHq94v5rZ78Bp8h0nhv7X1ICca42h8mBEn 1tb8SmfQKXWfa51urVqkB2p4T6wvRuQ= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-115-bbdNzgP6OZ2MpwAnUHp3YA-1; Wed, 18 May 2022 14:00:45 -0400 X-MC-Unique: bbdNzgP6OZ2MpwAnUHp3YA-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 8ABAD185A7BA; Wed, 18 May 2022 18:00:44 +0000 (UTC) Received: from fuller.cnet (ovpn-112-2.gru2.redhat.com [10.97.112.2]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 476E6492C14; Wed, 18 May 2022 18:00:44 +0000 (UTC) Received: by fuller.cnet (Postfix, from userid 1000) id 2433D41C3A1F; Wed, 18 May 2022 14:44:44 -0300 (-03) Date: Wed, 18 May 2022 14:44:44 -0300 From: Marcelo Tosatti To: Qian Cai Cc: Mel Gorman , Andrew Morton , Nicolas Saenz Julienne , Vlastimil Babka , Michal Hocko , LKML , Linux-MM Subject: Re: [PATCH 0/6] Drain remote per-cpu directly v3 Message-ID: References: <20220512085043.5234-1-mgorman@techsingularity.net> <20220517233507.GA423@qian> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.85 on 10.11.54.10 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 18, 2022 at 02:26:08PM -0300, Marcelo Tosatti wrote: > On Tue, May 17, 2022 at 07:35:07PM -0400, Qian Cai wrote: > > On Thu, May 12, 2022 at 09:50:37AM +0100, Mel Gorman wrote: > > > Changelog since v2 > > > o More conversions from page->lru to page->[pcp_list|buddy_list] > > > o Additional test results in changelogs > > > > > > Changelog since v1 > > > o Fix unsafe RT locking scheme > > > o Use spin_trylock on UP PREEMPT_RT > > > > > > This series has the same intent as Nicolas' series "mm/page_alloc: Remote > > > per-cpu lists drain support" -- avoid interference of a high priority > > > task due to a workqueue item draining per-cpu page lists. While many > > > workloads can tolerate a brief interruption, it may be cause a real-time > > > task runnning on a NOHZ_FULL CPU to miss a deadline and at minimum, > > > the draining in non-deterministic. > > > > > > Currently an IRQ-safe local_lock protects the page allocator per-cpu lists. > > > The local_lock on its own prevents migration and the IRQ disabling protects > > > from corruption due to an interrupt arriving while a page allocation is > > > in progress. The locking is inherently unsafe for remote access unless > > > the CPU is hot-removed. > > > > > > This series adjusts the locking. A spinlock is added to struct > > > per_cpu_pages to protect the list contents while local_lock_irq continues > > > to prevent migration and IRQ reentry. This allows a remote CPU to safely > > > drain a remote per-cpu list. > > > > > > This series is a partial series. Follow-on work should allow the > > > local_irq_save to be converted to a local_irq to avoid IRQs being > > > disabled/enabled in most cases. Consequently, there are some TODO comments > > > highlighting the places that would change if local_irq was used. However, > > > there are enough corner cases that it deserves a series on its own > > > separated by one kernel release and the priority right now is to avoid > > > interference of high priority tasks. > > > > Reverting the whole series fixed an issue that offlining a memory > > section blocking for hours on today's linux-next tree. > > > > __wait_rcu_gp > > synchronize_rcu at kernel/rcu/tree.c:3915 > > lru_cache_disable at mm/swap.c:886 > > __alloc_contig_migrate_range at mm/page_alloc.c:9078 > > isolate_single_pageblock at mm/page_isolation.c:405 > > start_isolate_page_range > > offline_pages > > memory_subsys_offline > > device_offline > > online_store > > dev_attr_store > > sysfs_kf_write > > kernfs_fop_write_iter > > new_sync_write > > vfs_write > > ksys_write > > __arm64_sys_write > > invoke_syscall > > el0_svc_common.constprop.0 > > do_el0_svc > > el0_svc > > el0t_64_sync_handler > > el0t_64_sync > > > > For full disclosure, I have also reverted the commit 0d523026abd4 > > ("mm/page_alloc: fix tracepoint mm_page_alloc_zone_locked()"), so the > > series can be reverted cleanly. But, I can't see how the commit > > 0d523026abd4 could cause this issue at all. > > Hi Qian, > > The issue is probably due to lack of the following: > > https://lore.kernel.org/linux-mm/YmrWK%2FKoU1zrAxPI@fuller.cnet/ > > Can you please give the patch on the URL a try? > > Thanks! Oops, sorry don't think the above URL has anything to do with this problem.