From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754196Ab3L3EIe (ORCPT ); Sun, 29 Dec 2013 23:08:34 -0500 Received: from moutng.kundenserver.de ([212.227.126.171]:49994 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753686Ab3L3EId (ORCPT ); Sun, 29 Dec 2013 23:08:33 -0500 Message-ID: <1388376508.5345.23.camel@marge.simpson.net> Subject: Re: [RFC] sched: update rq clock when only get preempt From: Mike Galbraith To: Lei Wen Cc: linux-kernel@vger.kernel.org, Peter Zijlstra , Ingo Molnar , leiwen@marvell.com Date: Mon, 30 Dec 2013 05:08:28 +0100 In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3 Content-Transfer-Encoding: 7bit Mime-Version: 1.0 X-Provags-ID: V02:K0:5CzbQumrnWhSFssxxnED/UylOUf5bdETxUCz8VqLta8 ThnGh6U3usfpjjZus+8Zc3iT4/mEntJnDbkyaJpntID27IfLEJ dBdUoiLGVjRYvOW7xAsPlTO4hSnE3BH3TnRrL2kyBOEhCdUme0 yt4aGRH2cOg7jIV0Eb1vfUM+BxkkGvE44OCQB5h0E3fW9xds3A kfUD26biTxqh09dxB8mmAKgf/W4aFYU100vWbcAK+VS4bi5NKj Gg6+4PkrML2Xk6AnX1DOfa98kNyjFS3v/E9MUG896vJA5pTx0b H9yDWyvb66zwXWoUgMD8spcxPvsEqnGx65sRCk/uQEhFldxU0O YCb8ZZFOBOpDd+lyWKnR+nuTS7/N9CtX/n7yC7XSRigHacQDeZ Utl4IuFywkcWg== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2013-12-30 at 11:14 +0800, Lei Wen wrote: > Since we would update rq clock at task enqueue/dequeue, or schedule > tick. If we don't update the rq clock when our previous task get > preempted, our new started task would get a relative stale rq clock > which is updated during the previous task enqueue, or the last schedule > clock update. > @@ -2555,6 +2556,8 @@ need_resched: > idle_balance(cpu, rq); > > put_prev_task(rq, prev); > + if (update) > + update_rq_clock(rq); If prev remained enqueued, the clock was updated by put_prev_task(). -Mike