Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262337AbUCSKaW (ORCPT ); Fri, 19 Mar 2004 05:30:22 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262456AbUCSKaW (ORCPT ); Fri, 19 Mar 2004 05:30:22 -0500 Received: from ns.suse.de ([195.135.220.2]:56803 "EHLO Cantor.suse.de") by vger.kernel.org with ESMTP id S262337AbUCSKaR (ORCPT ); Fri, 19 Mar 2004 05:30:17 -0500 Date: Fri, 19 Mar 2004 11:30:16 +0100 Message-ID: From: Takashi Iwai To: Andrew Morton Cc: andrea@suse.de, mjy@geizhals.at, linux-kernel@vger.kernel.org, Dipankar Sarma Subject: Re: CONFIG_PREEMPT and server workloads In-Reply-To: <20040318221006.74246648.akpm@osdl.org> References: <40591EC1.1060204@geizhals.at> <20040318060358.GC29530@dualathlon.random> <20040318110159.321754d8.akpm@osdl.org> <20040318221006.74246648.akpm@osdl.org> User-Agent: Wanderlust/2.10.1 (Watching The Wheels) SEMI/1.14.5 (Awara-Onsen) FLIM/1.14.5 (Demachiyanagi) APEL/10.6 MULE XEmacs/21.4 (patch 13) (Rational FORTRAN) (i386-suse-linux) MIME-Version: 1.0 (generated by SEMI 1.14.5 - "Awara-Onsen") Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1262 Lines: 36 At Thu, 18 Mar 2004 22:10:06 -0800, Andrew Morton wrote: > > Takashi Iwai wrote: > > > > BTW, i had the worst latency in sis900's timer handler. > > it takes 3ms, and hard to fix, too :-< > > It's all coming back to me now. > > The worst-case latency is during umount, fs/inode.c:invalidate_list() when > the filesystem has a zillion inodes in icache. Measured 250 milliseconds > on a 256MB 2.7GHz P4 here. OK, so don't do that. also that's not included in my test case :) > The unavoidable worst case is in the RCU callbacks for dcache shrinkage - > I've seen 25 millisecond holdoffs on the above machine during filesystem > stresstests when RCU is freeing a huge number of dentries in softirq > context. hmm, this wasn't also evaluated in my tests. it's worthy to try. thanks for the info. > This if Hard To Fix. Dipankar spent quite some time looking into it and > had patches, but I lost track of where they're at. couldn't this tasklet be replaced with workqueue or such? Takashi - 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/