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 23B9DC433EF for ; Wed, 18 May 2022 18:01:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241300AbiERSA4 (ORCPT ); Wed, 18 May 2022 14:00:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44266 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241274AbiERSAy (ORCPT ); Wed, 18 May 2022 14:00:54 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 3BB1828E33 for ; Wed, 18 May 2022 11:00:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1652896850; 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=sZ6XkqftPp6+2SO/U19yMkAzwiwGJ8gH141XFFjaMZE=; b=Zli3fe1oCRlC2yfmJmJKwh5a2km+ZR0r9+hIu0/IBCxBCxTDIbXILXoZ6CGrWMae1KeXOE tF5z/13QO9BrK6eVhrMyuXNExUa7GxJgLtzGPtxuDj/hY0i8CF2sH6GrVInYLhS6+POUhS XhXIxC7tDotq+uMlqwSa1DNJPvLMU8Q= 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-318-EQPSi9SHMQCc3qgclNXBrQ-1; Wed, 18 May 2022 14:00:45 -0400 X-MC-Unique: EQPSi9SHMQCc3qgclNXBrQ-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 85D7180B712; 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 48B83401E74; Wed, 18 May 2022 18:00:44 +0000 (UTC) Received: by fuller.cnet (Postfix, from userid 1000) id A7A3E41C3A1B; Wed, 18 May 2022 14:26:08 -0300 (-03) Date: Wed, 18 May 2022 14:26:08 -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: <20220517233507.GA423@qian> X-Scanned-By: MIMEDefang 2.85 on 10.11.54.10 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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!