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 14565C6FA8E for ; Thu, 2 Mar 2023 22:23:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229973AbjCBWXR (ORCPT ); Thu, 2 Mar 2023 17:23:17 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38848 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229966AbjCBWXO (ORCPT ); Thu, 2 Mar 2023 17:23:14 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9813A55527 for ; Thu, 2 Mar 2023 14:22:22 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1677795741; 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=an9MmHgGy0qzFZ8UIQUjGddxHR1f8bNnqbnky4ov8DU=; b=PD/yoAgDohl4hEgIpql5QGiX9rd3tAo8bNC6Xyt4mbxoGyuI+0MMlKMUP3KytL6/V+DGV0 M0SYuWt53L1t/PW8z1mTPOc12RXlJib5C7qqJm+LkcN2GPwsm7ZJwo9UEcqf1EQY8T3JBv OEYKWijU+x7bvg2TVpUz2slWlJoHZh0= Received: from mail-qv1-f69.google.com (mail-qv1-f69.google.com [209.85.219.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-297-t5LtG9rONcKnx67qbBJo4w-1; Thu, 02 Mar 2023 16:19:53 -0500 X-MC-Unique: t5LtG9rONcKnx67qbBJo4w-1 Received: by mail-qv1-f69.google.com with SMTP id l13-20020ad44d0d000000b004c74bbb0affso315507qvl.21 for ; Thu, 02 Mar 2023 13:19:53 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1677791993; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=an9MmHgGy0qzFZ8UIQUjGddxHR1f8bNnqbnky4ov8DU=; b=LA8Iuyfwy7eHBDP7Iy5ghhe4i9OVzd/ZyJr4oYHafxkl+HZ7YA3QA6H4TLugBfyXoU wn9y2m2NZ8N0vz0Cb2DLOtCu4sHcMOZSw7xGJOIG4H7T92+QbPHRlfQiWwQh556uV+qE IeRKL+khb/gP602BrSESELfEQqj4fsEQwgHkSgnlMrVnQzlDL/lUkJR+Qx4uaa1iJZGN izXOfgjIQZkZrToo+V9ageyUkaHP7QD4dBvih9I3zY5iuQEdPhO4+KYFVu8Pxz+OsTJ5 Ywvyw72HxyTsSjPIi8Vl8bYfsIu3daRa8zbT4v9aN/j+Wqqgm8OVy2g+ZvdgWx2j/vx4 rcQg== X-Gm-Message-State: AO0yUKV5i8LYrWFjDGxnGs3Yc4peI0so1lhVFTsna5G1vTUM+wfIelf4 iWtufeRogROStQTClJGrUqcovAFCY31X1QcG1+9fmi7Hv3GMjRGMQNGZb7E/CFiMOWf5fOd+k74 3CtDAygjc8ks3BE/K00IsC7tk6Xc0Rw== X-Received: by 2002:ac8:5c86:0:b0:3bf:b0c6:497b with SMTP id r6-20020ac85c86000000b003bfb0c6497bmr22379665qta.2.1677791992765; Thu, 02 Mar 2023 13:19:52 -0800 (PST) X-Google-Smtp-Source: AK7set8PF1hTlK8HTUITRVjlZRoMsJOKOmpk5rrOgeWX2x/xJfHaMGJ53hSke3jtLb29a+dxdnmWrw== X-Received: by 2002:ac8:5c86:0:b0:3bf:b0c6:497b with SMTP id r6-20020ac85c86000000b003bfb0c6497bmr22379633qta.2.1677791992505; Thu, 02 Mar 2023 13:19:52 -0800 (PST) Received: from x1n (bras-base-aurron9127w-grc-56-70-30-145-63.dsl.bell.ca. [70.30.145.63]) by smtp.gmail.com with ESMTPSA id bl14-20020a05620a1a8e00b00706bc44fda8sm398391qkb.79.2023.03.02.13.19.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 02 Mar 2023 13:19:51 -0800 (PST) Date: Thu, 2 Mar 2023 16:19:50 -0500 From: Peter Xu To: Marcelo Tosatti Cc: Christoph Lameter , Aaron Tomlin , Frederic Weisbecker , Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v2 09/11] mm/vmstat: use cmpxchg loop in cpu_vm_stats_fold Message-ID: References: <20230209150150.380060673@redhat.com> <20230209153204.873999366@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 02, 2023 at 10:55:09AM -0300, Marcelo Tosatti wrote: > > (2) If someone can modify the dead cpu's vm_stat_diff, > > The only context that can modify the cpu's vm_stat_diff are: > > 1) The CPU itself (increases the counter). > 2) cpu_vm_stats_fold (from vmstat_shepherd kernel thread), from > x -> 0 only. I think I didn't continue reading so I didn't see cpu_vm_stats_fold() will be reused when commenting, sorry. Now with a reworked (and SMP-safe) cpu_vm_stats_fold() and vmstats, I'm wondering the possibility of merging it with refresh_cpu_vm_stats() since they really look similar. IIUC the new refresh_cpu_vm_stats() logically doesn't need the small preempt disabled sections, not anymore, if with a cpu_id passed over to cpu_vm_stats_fold(), which seems to be even a good side effect. But not sure I missed something. -- Peter Xu