Received: by 2002:a25:c593:0:0:0:0:0 with SMTP id v141csp1570100ybe; Mon, 2 Sep 2019 23:53:04 -0700 (PDT) X-Google-Smtp-Source: APXvYqyHsdvQsGjjjnPMgJlwuVEmGQYUu0OGVi03OHijYuQF8Ym7wm5kB0VP8cRk9kseJ9U7ekA2 X-Received: by 2002:a63:d34c:: with SMTP id u12mr29113826pgi.114.1567493583877; Mon, 02 Sep 2019 23:53:03 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1567493583; cv=none; d=google.com; s=arc-20160816; b=qdqYK59ZXXizl3vlGtsDcAYJ3VgfDLhU5E9BIu5SS+3znvE3qtfIg7mkNfIjRVMnwg XXMa+WoVJd6qe0NNEPsaGIK2lCMachsTV1bBkrDPi7f6FRh1xc+Ru+LSCvmBn4T5yMCo cL9qne+HKHS/xQiMtv6lvNT1XngKkK30M6wj0oSJLZRXbefOUXSg96JCE+/qEcNnOubZ G42v4+pZOg2TBDtBBmKMHEoU/MZg9qnpOg2gmppGB+xAxltQ1e4M5H22aFMwuIAg42W4 knxHnx1Cwl+dTcRoN7Gf9woqSeLCzkY3XARfCkrZG5hsI7KrAkxQg2N4SvO9VOv+dwEu AlKw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:user-agent:in-reply-to :content-disposition:mime-version:references:message-id:subject:cc :to:from:date:dkim-signature; bh=on1uS5ivzDuDh9bGgt6qOTnzv59PRDx52jliN2T4+Mo=; b=0RVlxMNaS/RHDRbPnLheYuiy11mh426AbWSkCexrMrnzA/EBXbsL7ByGK073Qn2FUJ 6wGDwxsL84MU3qKeZXOOVkl4rM+EKZJvGzFvIesJ9UgbEUId9ZWJZJ5ls2VDHTd9ob5Q HFs5/OsjJcNuyOiHrwTSydT/GcS85W68x9/izXc1ZapuwziTYwC6JqViHCJU9XysDCub IpKDvxxy4/EHtEhGYHDBL9k5gMiuxyX1HlzxJUdqpma2lJWkX+dkgtF582B2mE7/SX4N 5GZRpT4Yp4pxy1xzjjbwH4/INwRY4icLkJml0XyVrvRprH8YhGosGlo6YKqgx8PNlFEm mHMA== ARC-Authentication-Results: i=1; mx.google.com; dkim=fail header.i=@infradead.org header.s=bombadil.20170209 header.b=D0b65z2+; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id 29si13794684pgk.306.2019.09.02.23.52.48; Mon, 02 Sep 2019 23:53:03 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=fail header.i=@infradead.org header.s=bombadil.20170209 header.b=D0b65z2+; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727284AbfICGv6 (ORCPT + 99 others); Tue, 3 Sep 2019 02:51:58 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:46744 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725878AbfICGv6 (ORCPT ); Tue, 3 Sep 2019 02:51:58 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=on1uS5ivzDuDh9bGgt6qOTnzv59PRDx52jliN2T4+Mo=; b=D0b65z2+nz0bUijDBcAL7blia KGLhVDc4Bdpo5lTzExmOhVr6xcJ2Q+FEcYmgis7Z+mT3YXjEKHrdOE6xtmUosvth6cQmx351LlTdX Oie7o3eEP0PPc3WI2mZgGxxG+SIeSAg4YcnUPvAbSEaU3tM2CKCOt3mPf//OU3S/2b4EyCcExd5iE MVatl0Xr+stxlGWhhU1eIa3vDxYN2DMNOU/2dDuWoopMnSmuO6xBYiS8tGW/ui5HecpjB3+/EYHJJ 7mBAXGBk124z43eTlwevOFs8Xwhu/p8WDiozAB2gIVMbf6UFZKqvb2b33/tNQ3haEPeGPhb8ip4VS l59g+y2lA==; Received: from hch by bombadil.infradead.org with local (Exim 4.92 #3 (Red Hat Linux)) id 1i52fT-0007ew-Ft; Tue, 03 Sep 2019 06:51:55 +0000 Date: Mon, 2 Sep 2019 23:51:55 -0700 From: Christoph Hellwig To: Alexey Dobriyan Cc: mingo@redhat.com, peterz@infradead.org, aarcange@redhat.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, rcu@vger.kernel.org, dm-devel@redhat.com, axboe@kernel.dk Subject: Re: [dm-devel] [PATCH] sched: make struct task_struct::state 32-bit Message-ID: <20190903065155.GA28322@infradead.org> References: <20190902210558.GA23013@avx2> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190902210558.GA23013@avx2> User-Agent: Mutt/1.11.4 (2019-03-13) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 03, 2019 at 12:05:58AM +0300, 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. I guess we'd save even more when moving from a volatile to WRITE_ONCE/READ_ONCE..