From owner-freebsd-hackers@FreeBSD.ORG Wed Dec 4 15:02:39 2013 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 2FAF9B2D; Wed, 4 Dec 2013 15:02:39 +0000 (UTC) Received: from mail-bk0-x232.google.com (mail-bk0-x232.google.com [IPv6:2a00:1450:4008:c01::232]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id 89915171B; Wed, 4 Dec 2013 15:02:38 +0000 (UTC) Received: by mail-bk0-f50.google.com with SMTP id e11so6655767bkh.37 for ; Wed, 04 Dec 2013 07:02:36 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=sender:message-id:date:from:user-agent:mime-version:to:cc:subject :references:in-reply-to:content-type:content-transfer-encoding; bh=dB3b8iuuA0FFkwnzYZRW74HC1VfjUSlC0SxeBjLkLsY=; b=PZZhdUQwTC+n/9PouXdP9DhMhR59wQ9nvSwEy6CUn+/kXfHRsVyL5ppLS0KoFucuK5 oUjnAqMbAAGZODd9yeK3BgM2QXW2rDE29+Sg6djb77Z7ohBNlh8jLaNmlRYi8AX3HOae IbvH1sn1ZPZl/Wwc3ruP824Ujjy2adTWjVYtR+R2pWQwr1Ht8CALuf/L5Z6vuqMWQrWF eOteyUENNlMF5Ovw4wmuK3lXmuKVEY3ogMK9ZRBdA3Hxz8Vn5mw+CZweYfZYmausiD/w GA4SwOYUsAjzJSlFLi3625SeC20qk8YTi09z/JJizpD1Gd+CzBMjFe/Fn+zCsU1jXF9a PQjw== X-Received: by 10.204.230.197 with SMTP id jn5mr90754bkb.127.1386169356522; Wed, 04 Dec 2013 07:02:36 -0800 (PST) Received: from mavbook.mavhome.dp.ua ([178.137.150.35]) by mx.google.com with ESMTPSA id o5sm29557401bkz.4.2013.12.04.07.02.34 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 04 Dec 2013 07:02:35 -0800 (PST) Sender: Alexander Motin Message-ID: <529F4409.9080403@FreeBSD.org> Date: Wed, 04 Dec 2013 17:02:33 +0200 From: Alexander Motin User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:24.0) Gecko/20100101 Thunderbird/24.1.0 MIME-Version: 1.0 To: Bret Ketchum Subject: Re: 9.1 callout behavior References: <5295A261.2060403@FreeBSD.org> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: "freebsd-hackers@freebsd.org" , Adrian Chadd X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.17 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 04 Dec 2013 15:02:39 -0000 On 04.12.2013 14:49, Bret Ketchum wrote: > See attached. I've tightened up the definition of inconsistent > callout calls. A "Whoops" message indicates the callout function was > called either side of a 10ms window than what was expected. "Ouch" > indicates the cyclecounter does not agree with the expected period given > the same 10ms fudge factor. I have this module running on two of my tests systems with stable/9 (2xE5645 and i7-3770) and half hour later I see no any of related messages on consoles. Could you share what exactly do you have there logged? > On Wed, Nov 27, 2013 at 3:28 AM, Bret Ketchum > wrote: > > Alexander, > > In this scenario, global ticks should have increased by 100 > every interval. When the wheels go off the truck, global ticks will > be 800+ yet only a fraction of usual number of clock cycles have > increased. > > I'll try to cook up an kernel module which will reproduce. > > > On Wed, Nov 27, 2013 at 1:42 AM, Alexander Motin > wrote: > > Hi, Brett, > > Could you tell more about "ticks has increased 8x"? Tickless > mode it is somewhat tricky algorithm to track global ticks > counter, but it should not jump that big. Jumps there could > easily trigger wrong callout behavior in 9 (in 10 callout code > was rewritten and no longer depend on ticks). > > > On 21.11.2013 22:19, Adrian Chadd wrote: > > It sounds like you may have found an interesting test case. > > Mav, any ideas? > > On 21 November 2013 05:20, Bret Ketchum > wrote: > > I've a callout which runs every 100ms and does a > bit of accounting > using the global ticks variable. This one-shot callout > was called fairly > consistently in 8.1, every 100ms give or take a few > thousand clocks. I've > recently upgraded to 9.1 and for the most part the > period is consistent. > However, periodically the callout function is executed > anywhere between 5ms > to 20ms after the callout was reset and the function > returned while global > ticks has increased 8x. The hardware has not changed > (using the same > timecounter configuration): > > CPU: Intel(R) Xeon(R) CPU E5-2640 0 @ 2.50GHz > (2500.05-MHz K8-class CPU) > > kern.timecounter.hardware: TSC-low > kern.timecounter.tick: 1 > kern.timecounter.invariant___tsc: 1 > kern.timecounter.smp_tsc: 1 > > And default eventtimer configuration: > > kern.eventtimer.singlemul: 2 > kern.eventtimer.idletick: 0 > kern.eventtimer.activetick: 1 > kern.eventtimer.timer: LAPIC > kern.eventtimer.periodic: 0 > > If tickless mode is disabled the inconsistency > goes away. Is the > premature expiration of the callout expected? Is the > jump in global ticks > typical (say from 100 ticks to 800 ticks in 1.5ms)? > > Bret > _________________________________________________ > freebsd-hackers@freebsd.org > mailing list > http://lists.freebsd.org/__mailman/listinfo/freebsd-__hackers > > To unsubscribe, send any mail to > "freebsd-hackers-unsubscribe@__freebsd.org > " > > > > -- > Alexander Motin > > > -- Alexander Motin