From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752647AbaAORLh (ORCPT ); Wed, 15 Jan 2014 12:11:37 -0500 Received: from merlin.infradead.org ([205.233.59.134]:43453 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751774AbaAORLd (ORCPT ); Wed, 15 Jan 2014 12:11:33 -0500 Date: Wed, 15 Jan 2014 18:10:37 +0100 From: Peter Zijlstra To: Oleg Nesterov Cc: "Paul E. McKenney" , linux-kernel@vger.kernel.org, mingo@kernel.org, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, darren@dvhart.com, fweisbec@gmail.com, sbw@mit.edu Subject: Re: [PATCH tip/core/timers 2/4] timers: Reduce __run_timers() latency for empty list Message-ID: <20140115171037.GK31570@twins.programming.kicks-ass.net> References: <20140115051939.GA31164@linux.vnet.ibm.com> <1389763248-31297-1-git-send-email-paulmck@linux.vnet.ibm.com> <1389763248-31297-2-git-send-email-paulmck@linux.vnet.ibm.com> <20140115170310.GB11499@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140115170310.GB11499@redhat.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 15, 2014 at 06:03:10PM +0100, Oleg Nesterov wrote: > On 01/14, Paul E. McKenney wrote: > > > > The __run_timers() function currently steps through the list one jiffy at > > a time > > And this is very suboptimal if jiffies - timer_jiffies is huge. Looks > like, we should rework base->tv* structures, or (perhaps) optimize > the "cascade" logic so that __run_timers() can increment timer_jiffies > and move all the expired timers into work_list at one step. And the > ->next_timer logic is obviously very suboptimal. Thomas is actually actively working on a replacement for the entire cascade mess.