From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755987AbYDXJwi (ORCPT ); Thu, 24 Apr 2008 05:52:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751489AbYDXJw3 (ORCPT ); Thu, 24 Apr 2008 05:52:29 -0400 Received: from bombadil.infradead.org ([18.85.46.34]:57429 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751408AbYDXJw2 (ORCPT ); Thu, 24 Apr 2008 05:52:28 -0400 Date: Thu, 24 Apr 2008 05:52:15 -0400 From: Christoph Hellwig To: Arjan van de Ven Cc: T David Chinner , Benjamin Herrenschmidt , Ingo Molnar , Andrew Morton , Linux Kernel Mailing List , Thomas Gleixner Subject: Re: x86: 4kstacks default Message-ID: <20080424095215.GA13088@infradead.org> References: <200804181737.m3IHbabI010051@hera.kernel.org> <20080418142934.38ce6bf4.akpm@linux-foundation.org> <20080419142329.GA5339@elte.hu> <1208928421.9060.22.camel@pasglop> <20080423233652.GT103491721@sgi.com> <20080423174516.0982a325@laptopd505.fenrus.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080423174516.0982a325@laptopd505.fenrus.org> User-Agent: Mutt/1.5.17 (2007-11-01) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 23, 2008 at 05:45:16PM -0700, Arjan van de Ven wrote: > THe good news is that direct reclaim is.. rare. > And I also doubt XFS is unique here; imagine the whole stacking thing on x86-64 just the same ... It's bad news actually. Beause it means the stack overflow happens totally random and hard to reproduce. And no, XFS is not unique there, any filesystem with a complex enough writeback path (aka extents + delalloc + smart allocator) will have to use quite a lot here. I'll be my 2 cent that ext4 one finished up will run into this just as likely. > I wonder if the direct reclaim path should avoid direct reclaim if the stack has only X bytes left. > (where the value of X is... well we can figure that one out later) Actually direct reclaim should be totally avoided for complex filesystems. It's horrible for the stack and for the filesystem writeout policy and ondisk allocation strategies.