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 X-Spam-Level: X-Spam-Status: No, score=-7.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id F03A6C433E9 for ; Mon, 8 Feb 2021 14:48:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B3BBB64E30 for ; Mon, 8 Feb 2021 14:48:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233002AbhBHOry (ORCPT ); Mon, 8 Feb 2021 09:47:54 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43852 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232083AbhBHOep (ORCPT ); Mon, 8 Feb 2021 09:34:45 -0500 Received: from mail-ej1-x633.google.com (mail-ej1-x633.google.com [IPv6:2a00:1450:4864:20::633]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 81894C061788 for ; Mon, 8 Feb 2021 06:34:01 -0800 (PST) Received: by mail-ej1-x633.google.com with SMTP id a9so25058305ejr.2 for ; Mon, 08 Feb 2021 06:34:01 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=Cw2bJezjxJXzUVOhX7h38EvcUGtOt4m/8Z18cKh11zE=; b=CKSXjVv/xg64+uJ7vm8UgYFjbhKvsVTlGpTEy/kGeHqhEKekoJAyrdvUPb4S64ptCK tSpe5V/OPUHp12qv9T/uAB6qTOvqLDauQaENBkKz32rXhUrxi+HZp0eXCneU5BPr/91I JMH4/DKkc3uevcoH+j6f6YjwNB8pRUjNAFdX/CkbH6HcM5uVLrR23VUeL3+/DUQPCS9z u2KJTQv78CxCPqteRjBqyR7vibJdL5tHanvaz6Cwq6c3d7NpdvBArMgm/vQu5Dy4/f1x 8bhmdWKRFR4VXFv7hOfWlafFilu6Bx32ENuDlGITq5rtNR7T43Zy2dDrfbaMZxk4zl2R ljLg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=Cw2bJezjxJXzUVOhX7h38EvcUGtOt4m/8Z18cKh11zE=; b=tGIKOy3G8wzRZ8i6YWPKQd3TCAqHUWb4lz9RjdhQakeg72kUcnfe0MiXoJOt51UJ6t ba85a32Hj1lnY8+yjbfbqe/4cdgZy1swjuq2y+7BkDYYxYF578KRZBW1oR6x2UmJafpD tlxF4PvnRr9Q7Q5GOtXMkOaeHbodBzUCu/Ov8OEUFjtVEu4OcRaXVJ0o2bWfLo9SqaG2 aD4ZkJRqBDwrjVupsudAD7I9L3FDLgusaqpgunee1XutoY/JyghxhhrBJ/KRDzsmJlSy R2RWkDTNMFtUJ7AXS1TS/bP3oE3D3dNSRaLpxGOTyFpcdQ6EpFBwlVyu2/gMan80OSw9 F8xA== X-Gm-Message-State: AOAM531FdtGQBp/udhlX8X6NbGkrKKa4LI51Vk7LbJQ34J779TfvCO2X LNjh6QIai0nj+gmfg1eX4A== X-Google-Smtp-Source: ABdhPJxYyHeWrwacfNGlS4E7cJrhjaIngAiadK1mA+3UYCAcNjd/2WLpXPsbPPb6n0UtwqffzjtSOg== X-Received: by 2002:a17:907:9702:: with SMTP id jg2mr17461438ejc.48.1612794840348; Mon, 08 Feb 2021 06:34:00 -0800 (PST) Received: from localhost.localdomain ([46.53.253.245]) by smtp.gmail.com with ESMTPSA id o11sm9520679eds.19.2021.02.08.06.33.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 08 Feb 2021 06:33:59 -0800 (PST) Date: Mon, 8 Feb 2021 17:33:58 +0300 From: Alexey Dobriyan To: Peter Zijlstra Cc: mingo@redhat.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/5] sched: make struct task_struct::state 32-bit Message-ID: <20210208143358.GB10066@localhost.localdomain> References: <20210206151832.GA487103@localhost.localdomain> 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 Mon, Feb 08, 2021 at 11:39:25AM +0100, Peter Zijlstra wrote: > On Sat, Feb 06, 2021 at 06:18:32PM +0300, Alexey Dobriyan wrote: > > 32-bit accesses are shorter than 64-bit accesses on x86_64. > > Nothing uses 64-bitness of struct task_struct::state. > > > > Propagate 32-bitness to other variables and functions. > > You're saving a handful of bytes, why? Eeh? To save handful of bytes. > > --- a/include/linux/sched.h > > +++ b/include/linux/sched.h > > @@ -655,7 +655,7 @@ struct task_struct { > > struct thread_info thread_info; > > #endif > > /* -1 unrunnable, 0 runnable, >0 stopped: */ > > - volatile long state; > > + volatile int state; > > A much larger, but probably more useful cleanup would be to get rid of > that volatile. volatile is separate patch. It is independent of ->state type. I didn't think about this specific volatile at all.