From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261369AbUEKCjj (ORCPT ); Mon, 10 May 2004 22:39:39 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261786AbUEKCjj (ORCPT ); Mon, 10 May 2004 22:39:39 -0400 Received: from fw.osdl.org ([65.172.181.6]:63968 "EHLO mail.osdl.org") by vger.kernel.org with ESMTP id S261369AbUEKCji (ORCPT ); Mon, 10 May 2004 22:39:38 -0400 Date: Mon, 10 May 2004 19:39:01 -0700 From: Andrew Morton To: Horst von Brand Cc: davidsen@tmr.com, linux-kernel@vger.kernel.org Subject: Re: 2.6.6-rc3-mm2 (4KSTACK) Message-Id: <20040510193901.59cebd6a.akpm@osdl.org> In-Reply-To: <200405102031.i4AKVXLg022041@eeyore.valparaiso.cl> References: <200405102031.i4AKVXLg022041@eeyore.valparaiso.cl> X-Mailer: Sylpheed version 0.9.7 (GTK+ 1.2.10; i386-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Horst von Brand wrote: > > Bill Davidsen said: > > [...] > > > I tried 4k stack, I couldn't measure any improvement in anything (as in > > no visible speedup or saving in memory). > > 4K stacks lets the kernel create new threads/processes as long as there is > free memory; with 8K stacks it needs two consecutive free page frames in > physical memory, when memory is fragmented (and large) they are hard to > come by... This is true to a surprising extent. A couple of weeks ago I observed my 256MB box freeing over 20MB of pages before it could successfully acquire a single 1-order page. That was during an updatedb run. And a 1-order GFP_NOFS allocation was actually livelocking, because !__GFP_FS allocations aren't allowed to enter dentry reclaim. Which is why VFS caches are now forced to use 0-order allocations.