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 561D1C4332F for ; Fri, 16 Dec 2022 16:39:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231871AbiLPQjZ (ORCPT ); Fri, 16 Dec 2022 11:39:25 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39064 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230329AbiLPQik (ORCPT ); Fri, 16 Dec 2022 11:38:40 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 77A8D2EF6C for ; Fri, 16 Dec 2022 08:37:54 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1671208673; 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=cWScWAvYep77Gyx4lnGZnuqfT5BE0PC8Gj9tWWazPyU=; b=anSj7N0AqrMUtbYX4umx9YKWejwDBBylzDi+BjzZZ6EA6om8Ua45gDz3Ei8qS30E6JxqNt B+Edjmcwpe6yOTp8rbaVwiZqWL5BGYw1DHczwqAYhrik+vcoY8Xu/0l9K7q5toRg579CIi 4/1OBKRuZt+dlUIpGxmQWh4qJ4PvE5o= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-16-Vl2fRmUEPNytzogjf9AdJQ-1; Fri, 16 Dec 2022 11:37:48 -0500 X-MC-Unique: Vl2fRmUEPNytzogjf9AdJQ-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 C93881C09070; Fri, 16 Dec 2022 16:37:47 +0000 (UTC) Received: from tpad.localdomain (ovpn-112-3.gru2.redhat.com [10.97.112.3]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 55632400F5A; Fri, 16 Dec 2022 16:37:47 +0000 (UTC) Received: by tpad.localdomain (Postfix, from userid 1000) id 1E8FF401A0FD8; Fri, 16 Dec 2022 13:16:09 -0300 (-03) Date: Fri, 16 Dec 2022 13:16:09 -0300 From: Marcelo Tosatti To: Frederic Weisbecker Cc: atomlin@redhat.com, cl@linux.com, tglx@linutronix.de, mingo@kernel.org, peterz@infradead.org, pauld@redhat.com, neelx@redhat.com, oleksandr@natalenko.name, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v9 3/5] mm/vmstat: manage per-CPU stats from CPU context when NOHZ full Message-ID: References: <20221206161826.698593151@redhat.com> <20221206162416.474800121@redhat.com> <20221214133302.GA1931356@lothringen> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221214133302.GA1931356@lothringen> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.10 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 14, 2022 at 02:33:02PM +0100, Frederic Weisbecker wrote: > On Tue, Dec 06, 2022 at 01:18:29PM -0300, Marcelo Tosatti wrote: > > static inline void vmstat_mark_dirty(void) > > { > > + int cpu = smp_processor_id(); > > + > > + if (tick_nohz_full_cpu(cpu) && !this_cpu_read(vmstat_dirty)) { > > + struct delayed_work *dw; > > + > > + dw = &per_cpu(vmstat_work, cpu); > > + if (!delayed_work_pending(dw)) { > > + unsigned long delay; > > + > > + delay = round_jiffies_relative(sysctl_stat_interval); > > + queue_delayed_work_on(cpu, mm_percpu_wq, dw, delay); > > Currently the vmstat_work is flushed on cpu_hotplug (CPUHP_AP_ONLINE_DYN). > vmstat_shepherd makes sure to not rearm it afterward. But now it looks > possible for the above to do that mistake? Don't think the mistake is an issue. In case of a queue_delayed_work_on being called after cancel_delayed_work_sync, either vmstat_update executes on the local CPU, or on a different CPU (after the bound kworkers have been moved). Each case is fine (see vmstat_update). > > + } > > + } > > this_cpu_write(vmstat_dirty, true); > > } > > @@ -2009,6 +2028,10 @@ static void vmstat_shepherd(struct work_ > > for_each_online_cpu(cpu) { > > struct delayed_work *dw = &per_cpu(vmstat_work, cpu); > > > > + /* NOHZ full CPUs manage their own vmstat flushing */ > > + if (tick_nohz_full_cpu(smp_processor_id())) > > It should be the remote CPU instead of the current one. Fixed.