linux-kernel - Re: x86: 4kstacks default

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Date:	Sun, 20 Apr 2008 23:40:42 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Daniel Hazelton <dhazelton@...er.net>
CC:	Arjan van de Ven <arjan@...radead.org>,
	Adrian Bunk <bunk@...nel.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Shawn Bohrer <shawn.bohrer@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: x86: 4kstacks default

Daniel Hazelton wrote:

> At 12 threads per request it'd only take about 4200 outstanding requests. That 
> is high, but I can see it happening.

If it happens it just won't work on 32bit.

> Just makes you sound foolish. Run the numbers yourself and you'll see that it 
> is easy for a machine running highly threaded code to easily hit 50K threads.

I ran the numbers and the numbers showed that you need > 1.5GB of lowmem
with a somewhat realistic scenario (32K per thread) at 50k threads. And
subtracting 4k from that 32k number won't make any significant
difference (still 1.3GB)

If you claim that works on a 32bit system with typically 300-600MB
lowmem available (which is also shared by other subsystem) I know who
sounds foolish.

-Andi
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