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[2620:137:e000::1:20]) by mx.google.com with ESMTP id p10-20020a170902e74a00b00188fc3a3fb1si9266380plf.184.2023.01.10.06.23.38; Tue, 10 Jan 2023 06:23:45 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=fumOUau6; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231996AbjAJOHX (ORCPT + 55 others); Tue, 10 Jan 2023 09:07:23 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58016 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233613AbjAJOHK (ORCPT ); Tue, 10 Jan 2023 09:07:10 -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 5E8EC11C24 for ; Tue, 10 Jan 2023 06:06:02 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1673359561; 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=L9zi9RalXX+v8RXF5p/DtEGhu0ZZ+UvkcK+8i6aWfa4=; b=fumOUau6JT311WxypR11sZh3mN3HK8S88p14u+TYsc3gxtUfkGBx0f7z74jcLljzCt2UTo uU57YiqP+uo0VfTwZiq/C6a/9LAOz3VC0v64c0oN188X/3+EQIhCJ7+qZKSLlCLDfRRKxO zf8v9d+e2f5zuph4hzNojevgHbRE3Y4= 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-590-6KuOp-ugNeuH5PpnU3dh4g-1; Tue, 10 Jan 2023 09:05:56 -0500 X-MC-Unique: 6KuOp-ugNeuH5PpnU3dh4g-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 31C121C0040E; Tue, 10 Jan 2023 14:05:56 +0000 (UTC) Received: from tpad.localdomain (ovpn-112-2.gru2.redhat.com [10.97.112.2]) by smtp.corp.redhat.com (Postfix) with ESMTPS id B931E492C14; Tue, 10 Jan 2023 14:05:55 +0000 (UTC) Received: by tpad.localdomain (Postfix, from userid 1000) id 44EDF4052FE9B; Tue, 10 Jan 2023 08:50:28 -0300 (-03) Date: Tue, 10 Jan 2023 08:50:28 -0300 From: Marcelo Tosatti To: Hillf Danton Cc: atomlin@atomlin.com, frederic@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v13 3/6] mm/vmstat: manage per-CPU stats from CPU context when NOHZ full Message-ID: References: <20230105125218.031928326@redhat.com> <20230106001244.4463-1-hdanton@sina.com> <20230106150154.4560-1-hdanton@sina.com> <20230107001529.4617-1-hdanton@sina.com> <20230110024356.336-1-hdanton@sina.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230110024356.336-1-hdanton@sina.com> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.9 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 10, 2023 at 10:43:56AM +0800, Hillf Danton wrote: > On 9 Jan 2023 11:12:49 -0300 Marcelo Tosatti > > > > Yes, but if you do not return to userspace, then the per-CPU vm > > statistics can be dirty indefinitely. > > Could you specify the reasons for failing to return to userspace, > given it is undesired intereference for the shepherd to queue work > on the isolated CPUs. Any system call that takes longer than the threshold to sync vmstats. Or a long running kernel thread, for example: https://stackoverflow.com/questions/65111483/long-running-kthread-and-synchronize-net