From owner-freebsd-hackers@FreeBSD.ORG Tue Nov 26 21:38:29 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 A65866AD; Tue, 26 Nov 2013 21:38:29 +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 598312038; Tue, 26 Nov 2013 21:38:29 +0000 (UTC) Received: by mail-qe0-f42.google.com with SMTP id b4so5581243qen.1 for ; Tue, 26 Nov 2013 13:38:28 -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=Uvg6LAyd7Tneo/GNGJgNqoRoXgl1sFIaKqKx7NJqgRQ=; b=z6sjT94PpB+d3SbMbTbjfeZXwvlTOg813IE9m9dH0zD1QFHMw7InxeDiM4vzgpJvne dpaZsXZU1pgfnm8/JlXBXaE9L4Y2uZBKO/JqT5NIzCaKgIzp+v0a4NlweRKclpe2CN5u CcuOpB+KshBI2t7cGDaoYRtzpcELrQeO+2ANCaAAVlR8Lyk17MHeLThtA06Jh+2dyDYa +xDzypuTPB34ktwkUOl0c8tzhsCXOgsA4UOB9adSIG0M8DLoyLckm25Bml/uvDq5wMNK 3U56SSd30BR+p3ddHuUbr/Zhbtse7LBgqZHY1INAwKs63tJ1Sg9tA0QCrAZapJYlc8E+ 1vww== MIME-Version: 1.0 X-Received: by 10.224.111.197 with SMTP id t5mr60564335qap.49.1385501908467; Tue, 26 Nov 2013 13:38:28 -0800 (PST) Sender: adrian.chadd@gmail.com Received: by 10.224.207.66 with HTTP; Tue, 26 Nov 2013 13:38:28 -0800 (PST) In-Reply-To: References: Date: Tue, 26 Nov 2013 13:38:28 -0800 X-Google-Sender-Auth: XzFEph49JqN-2af1I92zOyfs3F4 Message-ID: Subject: Re: 9.1 callout behavior From: Adrian Chadd To: Bret Ketchum Content-Type: text/plain; charset=ISO-8859-1 Cc: "freebsd-hackers@freebsd.org" , Alexander Motin 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: Tue, 26 Nov 2013 21:38:29 -0000 Yup! -a On 26 November 2013 04:10, Bret Ketchum wrote: > > Would there be any benefit in producing an example kernel module which > exhibits this behavior? > > > On Thu, Nov 21, 2013 at 2:19 PM, Adrian Chadd wrote: >> >> 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" > >