From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932978AbXCKEON (ORCPT ); Sat, 10 Mar 2007 23:14:13 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S933014AbXCKEON (ORCPT ); Sat, 10 Mar 2007 23:14:13 -0500 Received: from waste.org ([66.93.16.53]:43860 "EHLO waste.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932978AbXCKEON (ORCPT ); Sat, 10 Mar 2007 23:14:13 -0500 Date: Sat, 10 Mar 2007 22:01:32 -0600 From: Matt Mackall To: Con Kolivas Cc: linux-kernel , Andrew Morton , ck@vds.kolivas.org Subject: Re: RSDL-mm 0.28 Message-ID: <20070311040132.GS10394@waste.org> References: <20070311013506.GD10459@waste.org> <8cd998d50703101828l71fbec7bi9a819ad7b7fd9828@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8cd998d50703101828l71fbec7bi9a819ad7b7fd9828@mail.gmail.com> User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Mar 11, 2007 at 01:28:22PM +1100, Con Kolivas wrote: > >make -j 5 ccache > > beryl ok good awful > > galeon good good bad > > mp3 good good bad > > terminal good good bad/ok > > mouse good good bad/ok ... > >RSDL makes most of the noyield hit back in normal make and then some > >with ccache. Impressive. But ccache is still destroying interactivity > >somehow. The ccache effect is fairly visible even with non-parallel > >'make'. > > Ok I don't think there's any actual accounting problem here per se > (although I did just recently post a bugfix for rsdl however I think > that's unrelated). What I think is going on in the ccache testcase is > that all the work is being offloaded to kernel threads reading/writing > to/from the filesystem and the make is not getting any actual cpu > time. I don't see significant system time while this is happening. > This is "worked around" in mainline thanks to the testing for > sleeping on uninterruptible sleep in the interactivity estimator. What > I suspect is happening is kernel threads that are running nice -5 are > doing all the work on make's behalf in the setting of ccache since it > is mostly i/o bound. The reason for -nice values on kernel threads is > questionable anyway. Can you try renicing your kernel threads all to > nice 0 and see what effect that has? Obviously this doesn't need a > recompile, but is simple enough to implement in kthread code as a new > default. Sorry, little to no benefit. -- Mathematics is the supreme nostalgia of our time.