From owner-freebsd-hackers@FreeBSD.ORG Thu Nov 21 20:19:24 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 C33B58E9; Thu, 21 Nov 2013 20:19:24 +0000 (UTC) Received: from mail-qe0-x22a.google.com (mail-qe0-x22a.google.com [IPv6:2607:f8b0:400d:c02::22a]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id 77F40226B; Thu, 21 Nov 2013 20:19:24 +0000 (UTC) Received: by mail-qe0-f42.google.com with SMTP id t9so234688qeq.1 for ; Thu, 21 Nov 2013 12:19:23 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:sender:in-reply-to:references:date:message-id:subject :from:to:cc:content-type; bh=kpGDszWBrPsRKcq3ThWD4VaQexDymEzZEyTqFrjvITA=; b=Gu1JBQArnz+VfCZ2R4U+4lT/4Ss/35NRuLa52jOY0uUdoaoo9Zfm0dnUOJ0FdQBzHw YgKNuXphSf3xTl8PIz/WiGDTd0ltdC7VqQF64CN63ZIate0fIlTDjIvWT+w+Vvzqq+MZ GKqNvUHck8YM2sQ97zapx8kMyYJKeE5eH2kc1XyZxEeS/jkRVQF1aJ/KA80oLWtreUiY OO9nGC+FjvWgeMjMx80ohUp4GXGAfJKNg5JuFIRhA4r7X5ybmDA9LhLouCDYzQKmkxQv pT0+q9eosqojie96n/wA3nsaDb6dkylHmVRNFr0vyk6JmukMoSeq4mupRcOGObUY/1o6 R8LA== MIME-Version: 1.0 X-Received: by 10.49.59.70 with SMTP id x6mr14644774qeq.17.1385065163751; Thu, 21 Nov 2013 12:19:23 -0800 (PST) Sender: adrian.chadd@gmail.com Received: by 10.224.207.66 with HTTP; Thu, 21 Nov 2013 12:19:23 -0800 (PST) In-Reply-To: References: Date: Thu, 21 Nov 2013 12:19:23 -0800 X-Google-Sender-Auth: KpSA66aqysuZ2E9gne5DjdMEl1E Message-ID: Subject: Re: 9.1 callout behavior From: Adrian Chadd To: Bret Ketchum , Alexander Motin Content-Type: text/plain; charset=ISO-8859-1 Cc: "freebsd-hackers@freebsd.org" X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.16 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 21 Nov 2013 20:19:24 -0000 Hi, It sounds like you may have found an interesting test case. Mav, any ideas? -adrian 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"