From owner-freebsd-fs@FreeBSD.ORG Wed Jun 1 14:55:54 2011 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 76F06106564A; Wed, 1 Jun 2011 14:55:54 +0000 (UTC) (envelope-from artemb@gmail.com) Received: from mail-gw0-f54.google.com (mail-gw0-f54.google.com [74.125.83.54]) by mx1.freebsd.org (Postfix) with ESMTP id 1ADCE8FC14; Wed, 1 Jun 2011 14:55:53 +0000 (UTC) Received: by gwb15 with SMTP id 15so3367449gwb.13 for ; Wed, 01 Jun 2011 07:55:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type; bh=Ul/33iDx1oNPNA9nayXMqeU41vdtz2lbtCITGakEVA4=; b=aJ3gI4WdEAuik+kVTRNJlMHestauvv0jm2gZ3APha6ezApKSSX9nkY3cVNRayI23YM Pfa5e48E1QhckRybLcM6VhyNCyfefxzJ4glkjYoSOH40uP0crKb5DthH67g6VqU/a9lO wkzS9EqtJQ9if/4wRnvIEnBYNLUjWc/HSYSyY= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type; b=a5rM6+0efI0TJ7KX9Anus/QVyKktsWg5V3buHDun7zw4A6ItcNErsncrVFqpnFR8D0 wpxB/9TDkG884xvDij40p/J519N2vvmN2inmcMTofo1G9TOA6JmE/VLej2+wOM1wbm/C r0xn6ncVzcZtr09lO6OWGT206IfFhxaLI0l5s= MIME-Version: 1.0 Received: by 10.236.193.105 with SMTP id j69mr6003032yhn.384.1306940153095; Wed, 01 Jun 2011 07:55:53 -0700 (PDT) Sender: artemb@gmail.com Received: by 10.236.208.70 with HTTP; Wed, 1 Jun 2011 07:55:53 -0700 (PDT) In-Reply-To: <4DE64D45.5060100@FreeBSD.org> References: <0EFD28CD-F2E9-4AE2-B927-1D327EC99DB9@bitgravity.com> <4DE50811.5060606@FreeBSD.org> <4DE51DD3.6040602@FreeBSD.org> <4DE64D45.5060100@FreeBSD.org> Date: Wed, 1 Jun 2011 07:55:53 -0700 X-Google-Sender-Auth: u-yUCLhvlA86JexNR39zUYDDb2o Message-ID: From: Artem Belevich To: Andriy Gapon Content-Type: text/plain; charset=ISO-8859-1 Cc: freebsd-fs@freebsd.org Subject: Re: ZFS: arc_reclaim_thread running 100%, 8.1-RELEASE, LBOLT related X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 01 Jun 2011 14:55:54 -0000 On Wed, Jun 1, 2011 at 7:31 AM, Andriy Gapon wrote: > on 31/05/2011 22:21 Artem Belevich said the following: >> On Tue, May 31, 2011 at 12:07 PM, David P Discher wrote: >>> And from the conversation on this thread, there isn't any agreement on how to really fix it. >> Andriy has proposed potential fix that would eliminate multiplication >> of gethrtime result by hz and would delay overflow by few hundred >> years. Should be good enough. > > Yeah, and here is a patch that implements the proposal (for head): > http://people.freebsd.org/~avg/osol-lbolt.diff I would keep nsec_per_tick as a static local variable in ddi_get_lbolt64 and init it conditionally if it's zero for the sake of keeping all the magic in once place. I have a hypothetical question. In a non-tickless kernel there is a natural limit on hz imposed by overhead of processing periodis interrupts. Now that we're event-driven, is there any chance that hz could grow larger than 1000000? --Artem