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Date: Mon, 21 Apr 2008 16:31:45 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Eric Sandeen <sandeen@sandeen.net>
Cc: Andrew Morton <akpm@linux-foundation.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Arjan van de Ven <arjan@infradead.org>,
       Thomas Gleixner <tglx@linutronix.de>
Subject: Re: x86: 4kstacks default
Message-ID: <20080421143145.GW9554@elte.hu>
References: <200804181737.m3IHbabI010051@hera.kernel.org> <20080418142934.38ce6bf4.akpm@linux-foundation.org> <20080419142329.GA5339@elte.hu> <480AB88C.1050900@sandeen.net>
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* Eric Sandeen <sandeen@sandeen.net> wrote:

> > and we've conducted tens of thousands of bootup tests with all sorts 
> > of drivers and kernel options enabled and have yet to see a single 
> > crash due to 4K stacks.
> 
> Really, not one?
> 
> https://bugzilla.redhat.com/show_bug.cgi?id=247158
> https://bugzilla.redhat.com/show_bug.cgi?id=227331
> https://bugzilla.redhat.com/show_bug.cgi?id=240077
> 
> (hehe, ok, xfs is a common component there...)
> 
> and it's not always obvious that you've overflowed the stack.
> 
> CONFIG_DEBUG_STACKOVERFLOW isn't ery useful because the warning printk 
> it generates uses the remaining amount of stack, and tips the box.

note that in -rt we have an ftrace plugin that measures _precise_ stack 
footprint, when it happens.

so it's possible to measure exact stack footprint and save a stack trace 
when that happens.

	Ingo