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 S1752861AbcFNUep (ORCPT <rfc822;w@1wt.eu>);
	Tue, 14 Jun 2016 16:34:45 -0400
Received: from bombadil.infradead.org ([198.137.202.9]:50414 "EHLO
	bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1751597AbcFNUen (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Tue, 14 Jun 2016 16:34:43 -0400
Date: Tue, 14 Jun 2016 22:34:34 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Arjan van de Ven <arjanvandeven@gmail.com>, Ingo Molnar <mingo@kernel.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: <20160614203434.GH30154@twins.programming.kicks-ass.net>
References: <20160613070440.950649741@linutronix.de>
 <20160613075929.282143900@linutronix.de>
 <20160613114005.GY30909@twins.programming.kicks-ass.net>
 <alpine.DEB.2.11.1606131426330.5839@nanos>
 <20160614101144.GA849@gmail.com>
 <alpine.DEB.2.11.1606141213300.5839@nanos>
 <CADyApD1L48AVT7D94wYuL89m7V+--rg59GFvHzhHMZ5uhhdaYw@mail.gmail.com>
 <alpine.DEB.2.11.1606142000150.5839@nanos>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <alpine.DEB.2.11.1606142000150.5839@nanos>
User-Agent: Mutt/1.5.23.1 (2014-03-12)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Tue, Jun 14, 2016 at 08:05:49PM +0200, Thomas Gleixner wrote:
> On Tue, 14 Jun 2016, Arjan van de Ven wrote:
> 
> > evaluating a 120 hours timer ever 37 hours to see if it should fire...
> > not too horrid.
> 
> Well that thing is doing weird stuff anyway:
> 
>    swapper     0 [001] 1789995.305532: timer:timer_start: timer=0xffff8800c8346920 function=death_by_timeout expires=4850639994 [timeout=108000000]

You're running a HZ=250 kernel, right?

inet/netfilter/nf_conntrack_proto_tcp.c:

#define SECS * HZ
#define MINS * 60 SECS
#define HOURS * 60 MINS
#define DAYS * 24 HOURS

static unsigned int tcp_timeouts[TCP_CONNTRACK_TIMEOUT_MAX] __read_mostly = {
	[TCP_CONNTRACK_SYN_SENT]	= 2 MINS,
	[TCP_CONNTRACK_SYN_RECV]	= 60 SECS,
	[TCP_CONNTRACK_ESTABLISHED]	= 5 DAYS,

					  ^^^^^^ that
ends up being 108000000 for HZ == 250.


	[TCP_CONNTRACK_FIN_WAIT]	= 2 MINS,
	[TCP_CONNTRACK_CLOSE_WAIT]	= 60 SECS,
	[TCP_CONNTRACK_LAST_ACK]	= 30 SECS,
	[TCP_CONNTRACK_TIME_WAIT]	= 2 MINS,
	[TCP_CONNTRACK_CLOSE]		= 10 SECS,
	[TCP_CONNTRACK_SYN_SENT2]	= 2 MINS,
/* RFC1122 says the R2 limit should be at least 100 seconds.
   Linux uses 15 packets as limit, which corresponds
   to ~13-30min depending on RTO. */
	[TCP_CONNTRACK_RETRANS]		= 5 MINS,
	[TCP_CONNTRACK_UNACK]		= 5 MINS,
};


>              ssh  3870 [001] 1790025.284704: timer:timer_cancel: timer=0xffff8800c8346920
>              ssh  3870 [001] 1790025.284707: timer:timer_start: timer=0xffff8800c8346920 function=death_by_timeout expires=4742722493 [timeout=75000]

And that one would then be one of the 5 MINS ones.