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=-5.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 6094FC3A5A2 for ; Tue, 3 Sep 2019 17:29:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 374D421897 for ; Tue, 3 Sep 2019 17:29:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728679AbfICR3K (ORCPT ); Tue, 3 Sep 2019 13:29:10 -0400 Received: from foss.arm.com ([217.140.110.172]:41538 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728571AbfICR3J (ORCPT ); Tue, 3 Sep 2019 13:29:09 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 52AB3360; Tue, 3 Sep 2019 10:29:09 -0700 (PDT) Received: from [10.1.194.37] (e113632-lin.cambridge.arm.com [10.1.194.37]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 3302E3F59C; Tue, 3 Sep 2019 10:29:08 -0700 (PDT) Subject: Re: [PATCH] sched: make struct task_struct::state 32-bit To: Alexey Dobriyan , mingo@redhat.com, peterz@infradead.org Cc: linux-kernel@vger.kernel.org, rcu@vger.kernel.org, linux-block@vger.kernel.org, dm-devel@redhat.com, axboe@kernel.dk, aarcange@redhat.com References: <20190902210558.GA23013@avx2> From: Valentin Schneider Message-ID: Date: Tue, 3 Sep 2019 18:29:06 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190902210558.GA23013@avx2> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: rcu-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org On 02/09/2019 22:05, Alexey Dobriyan wrote: > 32-bit accesses are shorter than 64-bit accesses on x86_64. > Nothing uses 64-bitness of ->state. > > Space savings are ~2KB on F30 kernel config. > > Signed-off-by: Alexey Dobriyan > --- > > arch/ia64/kernel/perfmon.c | 4 ++-- > block/blk-mq.c | 2 +- > drivers/md/dm.c | 4 ++-- > fs/userfaultfd.c | 2 +- > include/linux/sched.h | 6 +++--- > include/linux/sched/debug.h | 2 +- > include/linux/sched/signal.h | 2 +- > kernel/freezer.c | 2 +- > kernel/kthread.c | 4 ++-- > kernel/locking/mutex.c | 6 +++--- > kernel/locking/semaphore.c | 2 +- > kernel/rcu/rcutorture.c | 4 ++-- > kernel/rcu/tree_stall.h | 6 +++--- > kernel/sched/core.c | 8 ++++---- > lib/syscall.c | 2 +- > 15 files changed, 28 insertions(+), 28 deletions(-) > It looks like you missed a few places. There's a long prev_state in sched/core.c::finish_task_switch() for instance. I suppose that's where coccinelle oughta help but I'm really not fluent in that. Is there a way to make it match p.state accesses with p task_struct? And if so, can we make it change the type of the variable being read from / written to? How did you come up with this changeset, did you pickaxe for some regexp? [...]