linux-kernel - Re: [Announce] [patch] Modular Scheduler Core and Completely Fair Scheduler [CFS]

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Message-ID: <20070414161927.GD3099@elte.hu>
Date:	Sat, 14 Apr 2007 18:19:27 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Willy Tarreau <w@....eu>
Cc:	Nick Piggin <npiggin@...e.de>, linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Con Kolivas <kernel@...ivas.org>,
	Mike Galbraith <efault@....de>,
	Arjan van de Ven <arjan@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Jiri Slaby <jirislaby@...il.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [Announce] [patch] Modular Scheduler Core and Completely Fair Scheduler [CFS]


* Willy Tarreau <w@....eu> wrote:

> On Sat, Apr 14, 2007 at 03:01:01PM +0200, Willy Tarreau wrote:
> > 
> > Well, I'll stop heating the room for now as I get out of ideas about how
> > to defeat it.
> 
> Ah, I found something nasty.
> If I start large batches of processes like this :
> 
> $ for i in $(seq 1 1000); do ./scheddos2 4000 4000 & done
> 
> the ramp up slows down after 700-800 processes, but something very 
> strange happens. If I'm under X, I can switch the focus to all xterms 
> (the WM is still alive) but all xterms are frozen. On the console, 
> after one moment I simply cannot switch to another VT anymore while I 
> can still start commands locally. But "chvt 2" simply blocks. SysRq-K 
> killed everything and restored full control. Dmesg shows lots of :

> SAK: killed process xxxx (scheddos2): process_session(p)==tty->session.
> 
> I wonder if part of the problem would be too many processes bound to 
> the same tty :-/

hm, that's really weird. I've Cc:-ed the tty experts (Erik, Jiri, Alan), 
maybe this description rings a bell with them?

	Ingo
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