Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761931AbXHEUyt (ORCPT ); Sun, 5 Aug 2007 16:54:49 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753498AbXHEUym (ORCPT ); Sun, 5 Aug 2007 16:54:42 -0400 Received: from smtp2.linux-foundation.org ([207.189.120.14]:45338 "EHLO smtp2.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752394AbXHEUym (ORCPT ); Sun, 5 Aug 2007 16:54:42 -0400 Date: Sun, 5 Aug 2007 13:54:03 -0700 From: Andrew Morton To: Luca Tettamanti Cc: Jeff Dike , LKML Subject: Re: [PATCH 4/5] UML - Simplify helper stack handling Message-Id: <20070805135403.3c812dda.akpm@linux-foundation.org> In-Reply-To: <20070805204114.GA19857@dreamland.darkstar.lan> References: <20070614202655.GA9647@c2.user-mode-linux.org> <20070627233701.8e53f3cb.akpm@linux-foundation.org> <20070805204114.GA19857@dreamland.darkstar.lan> X-Mailer: Sylpheed 2.4.1 (GTK+ 2.8.17; x86_64-unknown-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 Content-Length: 2487 Lines: 60 On Sun, 5 Aug 2007 22:41:14 +0200 Luca Tettamanti wrote: > Il Wed, Jun 27, 2007 at 11:37:01PM -0700, Andrew Morton ha scritto: > > > > So I'm running the generic version of this on i386 with 8k stacks (below), > > with a quick LTP run. > > > > Holy cow, either we use a _lot_ of stack or these numbers are off: > > > > vmm:/home/akpm> dmesg -s 1000000|grep 'bytes left' > > khelper used greatest stack depth: 7176 bytes left > > khelper used greatest stack depth: 7064 bytes left > > khelper used greatest stack depth: 6840 bytes left > > khelper used greatest stack depth: 6812 bytes left > > hostname used greatest stack depth: 6636 bytes left > > uname used greatest stack depth: 6592 bytes left > > uname used greatest stack depth: 6284 bytes left > > hotplug used greatest stack depth: 5568 bytes left > > rpc.nfsd used greatest stack depth: 5136 bytes left > > chown02 used greatest stack depth: 4956 bytes left > > fchown01 used greatest stack depth: 4892 bytes left > > > > That's the sum of process stack and interrupt stack, but I doubt if this > > little box is using much interrupt stack space. > > > > No wonder people are still getting stack overflows with 4k stacks... > > Hi Andrew, > I was a bit worried about stack usage on my setup and google found your > mail :P > > FYI: > > khelper used greatest stack depth: 3228 bytes left > khelper used greatest stack depth: 3124 bytes left > busybox used greatest stack depth: 2808 bytes left > modprobe used greatest stack depth: 2744 bytes left > busybox used greatest stack depth: 2644 bytes left > modprobe used greatest stack depth: 1836 bytes left > modprobe used greatest stack depth: 1176 bytes left > java used greatest stack depth: 932 bytes left > java used greatest stack depth: 540 bytes left > > I'm running git-current, with 4KiB stacks; filesystems are ext3 and XFS > on LVM (on libata devices). > Does it make sense to raise STACK_WARN to get a stack trace in do_IRQ? > Or is 540 bytes still "safe" taking into account the separate IRQ stack? > 540 bytes free means that we've used 90% of the stack. I'd say it is extremely unsafe. Unbelieveably unsafe. I'm suspecting that the instrumentation is lying to us for some reason. - 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/