From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1752168AbcFNKLv (ORCPT <rfc822;w@1wt.eu>);
	Tue, 14 Jun 2016 06:11:51 -0400
Received: from mail-wm0-f66.google.com ([74.125.82.66]:35389 "EHLO
	mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1751494AbcFNKLt (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Tue, 14 Jun 2016 06:11:49 -0400
Date: Tue, 14 Jun 2016 12:11:45 +0200
From: Ingo Molnar <mingo@kernel.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>, LKML <linux-kernel@vger.kernel.org>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Eric Dumazet <edumazet@google.com>,
        Frederic Weisbecker <fweisbec@gmail.com>, Chris Mason <clm@fb.com>,
        Arjan van de Ven <arjan@infradead.org>, rt@linutronix.de,
        Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [patch 13/20] timer: Switch to a non cascading wheel
Message-ID: <20160614101144.GA849@gmail.com>
References: <20160613070440.950649741@linutronix.de>
 <20160613075929.282143900@linutronix.de>
 <20160613114005.GY30909@twins.programming.kicks-ass.net>
 <alpine.DEB.2.11.1606131426330.5839@nanos>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <alpine.DEB.2.11.1606131426330.5839@nanos>
User-Agent: Mutt/1.5.24 (2015-08-30)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org


* Thomas Gleixner <tglx@linutronix.de> wrote:

> On Mon, 13 Jun 2016, Peter Zijlstra wrote:
> > On Mon, Jun 13, 2016 at 08:41:00AM -0000, Thomas Gleixner wrote:
> > > +
> > > +	/* Cascading, sigh... */
> > 
> > So given that userspace has no influence on timer period; can't we
> > simply fail to support timers longer than 30 minutes?
> > 
> > In anything really arming timers _that_ long?
> 
> Unfortunately yes. Networking being one of those. Real cascading happens once
> in a blue moon, but it happens.

So I'd really prefer it if we added a few more levels, a hard limit and got rid of 
the cascading once and for all!

IMHO 'once in a blue moon' code is much worse than a bit more data overhead.

Thanks,

	Ingo