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[209.132.180.67]) by mx.google.com with ESMTP id d20-v6si4933914pgb.682.2018.07.19.03.50.24; Thu, 19 Jul 2018 03:51:02 -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=merlin.20170209 header.b=kY3mNtZO; 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 S1730813AbeGSLbd (ORCPT + 99 others); Thu, 19 Jul 2018 07:31:33 -0400 Received: from merlin.infradead.org ([205.233.59.134]:35596 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726475AbeGSLbd (ORCPT ); Thu, 19 Jul 2018 07:31:33 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.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=SQmo12u6GiJDyyohF2e8mRr73/YAIAu4hi1Khuvgq9o=; b=kY3mNtZO2QP+Lcqsak41YU/70 y7U3R76DRh2Rf2pdfG8hhmVoCkYSNqEHDDRHPnHkMfRs9FRBsZBGUFdAjgvxSWQ+TDh6a8ZEkwRjV /lkA+gW5rTjTqPqvdXqVvdODPkpA2U75Xs28nq6oK52iv5wd5i/fjw3MpjFxhrP/OelOIC6SHnps5 +2jWHHjokk+AFJed8yn7wHzw3G73toX1cYk4h0o+3hwznbgx1LB/jEbEXuiyep0n9w2LiOfsB3pYC DolsxSGHB7XqmFOuCNKJUyzmKedQ5+3gLz6VxskhJOZF1xLkFajpY2Ame0rHeJfRkyliTNXRNmgNz 0WIyffmwQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1fg6UB-0002cr-U0; Thu, 19 Jul 2018 10:48:40 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id A5A7220289330; Thu, 19 Jul 2018 12:48:38 +0200 (CEST) Date: Thu, 19 Jul 2018 12:48:38 +0200 From: Peter Zijlstra To: Pavel Tatashin Cc: steven.sistare@oracle.com, daniel.m.jordan@oracle.com, linux@armlinux.org.uk, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, john.stultz@linaro.org, sboyd@codeaurora.org, x86@kernel.org, linux-kernel@vger.kernel.org, mingo@redhat.com, tglx@linutronix.de, hpa@zytor.com, douly.fnst@cn.fujitsu.com, prarit@redhat.com, feng.tang@intel.com, pmladek@suse.com, gnomes@lxorguk.ukuu.org.uk, linux-s390@vger.kernel.org, boris.ostrovsky@oracle.com, jgross@suse.com, pbonzini@redhat.com Subject: Re: [PATCH v14 25/25] sched: use static key for sched_clock_running Message-ID: <20180719104838.GC2494@hirez.programming.kicks-ass.net> References: <20180718022211.6259-1-pasha.tatashin@oracle.com> <20180718022211.6259-26-pasha.tatashin@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180718022211.6259-26-pasha.tatashin@oracle.com> User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 17, 2018 at 10:22:11PM -0400, Pavel Tatashin wrote: > sched_clock_running may be read every time sched_clock_cpu() is called. > Yet, this variable is updated only twice during boot, and never changes > again, therefore it is better to make it a static key. Right, so the focus was always on making the sane TSC case fast, and if TSC isn't stable we'd just make do and not care too much. But this certainly isn't wrong, so ACK.