Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Wed, 23 Jan 2002 23:21:30 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Wed, 23 Jan 2002 23:21:10 -0500 Received: from [216.70.178.182] ([216.70.178.182]:4736 "EHLO mail.xinetd.com") by vger.kernel.org with ESMTP id ; Wed, 23 Jan 2002 23:21:09 -0500 Date: Wed, 23 Jan 2002 20:20:46 -0800 (PST) From: Glendon Gross To: Robert Love cc: Dan Maas , linux-kernel@vger.kernel.org Subject: Re: Low latency for recent kernels In-Reply-To: <1011845875.7028.63.camel@phantasy> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Is this patch available for 2.5.2 ? or is it already part of the tree? On 23 Jan 2002, Robert Love wrote: > On Wed, 2002-01-23 at 22:48, Dan Maas wrote: > > > Two situations where I would expect low-latency/preemption to have a > > positive effect on responsiveness are 1) when the system is under heavy CPU > > and disk load (e.g. kernel compile); due to the interactive tasks being able > > to run earlier/more often, and 2) when performing UI operations that depend > > on tight synchronization between X/the WM/the X client, particularly opaque > > window resizing. (my theory is that low-latency/preemption results in the > > CPU switching more rapidly or evenly among these processes, reducing the > > perceptible "lag" between the client window and its WM frame) > > This is exactly the area preempt/low-latency helps and I think your > theory is pretty much dead on. > > With preempt-kernel, ideally, an interactive task finds itself runnable > like this: user event causes interrupt, interrupt sets need_resched, on > return from interrupt we cause a preemption of current task (which can > happen whether task is in kernel or userland, now), and schedule the > interactive task onto the CPU. > > This leads to better scheduling fairness and short scheduling latency. > > If you or Havoc are interested in any tests or further work with the > preemptive kernel, I'd be more than willing. Hey, I use GNOME ;) > > Robert Love > > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/