From owner-freebsd-arch@FreeBSD.ORG Sat Jun 11 23:09:31 2011 Return-Path: Delivered-To: freebsd-arch@FreeBSD.ORG Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 95A7F1065675; Sat, 11 Jun 2011 23:09:31 +0000 (UTC) (envelope-from imp@bsdimp.com) Received: from harmony.bsdimp.com (bsdimp.com [199.45.160.85]) by mx1.freebsd.org (Postfix) with ESMTP id 347C08FC18; Sat, 11 Jun 2011 23:09:31 +0000 (UTC) Received: from [10.0.0.63] (63.imp.bsdimp.com [10.0.0.63]) (authenticated bits=0) by harmony.bsdimp.com (8.14.4/8.14.3) with ESMTP id p5BN7SAx057707 (version=TLSv1/SSLv3 cipher=DHE-DSS-AES128-SHA bits=128 verify=NO); Sat, 11 Jun 2011 17:07:31 -0600 (MDT) (envelope-from imp@bsdimp.com) Mime-Version: 1.0 (Apple Message framework v1084) Content-Type: text/plain; charset=us-ascii From: Warner Losh In-Reply-To: <20110611204326.GA51320@zim.MIT.EDU> Date: Sat, 11 Jun 2011 17:07:24 -0600 Content-Transfer-Encoding: quoted-printable Message-Id: References: <20110611171834.GA38142@zim.MIT.EDU> <20110611204326.GA51320@zim.MIT.EDU> To: David Schultz X-Mailer: Apple Mail (2.1084) X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.0.1 (harmony.bsdimp.com [10.0.0.6]); Sat, 11 Jun 2011 17:07:31 -0600 (MDT) Cc: mdf@FreeBSD.ORG, Adrian Chadd , freebsd-arch@FreeBSD.ORG Subject: Re: [RFC] shipping kernels with default modules? X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 11 Jun 2011 23:09:31 -0000 On Jun 11, 2011, at 2:43 PM, David Schultz wrote: > On Sat, Jun 11, 2011, mdf@freebsd.org wrote: >> On Sat, Jun 11, 2011 at 10:18 AM, David Schultz = wrote: >>> On Sat, Jun 11, 2011, Adrian Chadd wrote: >>>> Hi guys, >>>>=20 >>>> Has there been any further thought as of late about shipping = kernels >>>> with modules only by default, rather than monolithic kernels? >>>>=20 >>>> I tried this experiment a couple years ago and besides a little >>>> trickery with ACPI module loading, it worked out fine. >>>>=20 >>>> Is there any reason we aren't doing this at the moment? Eg by = having a >>>> default loader modules list populated from the kernel config file? >>>=20 >>> I've been doing this for years, and it has come in quite handy. >>> For instance, when my if_msk gets wedged, the only way to fix it >>> short of rebooting seems to be reloading the driver. >>>=20 >>> One issue, however, is that the boot loader is horrendously slow >>> at loading modules. (Either that or my BIOS has a braindead int 13h >>> handler.) Most of these modules aren't actually needed until much >>> later in the boot process, so a mechanism to load non-essential >>> modules after the file systems are mounted might provide a good >>> solution. >>=20 >> Indeed, at $WORK we're trying to get shutdown -> restart under 2 >> minutes. Several seconds of this is moving things *into* the kernel >> that need to be there (disk drivers), and everything else to a point >> in init where modules can be loaded in parallel, using the faster = disk >> driver, rather than in serial with slow BIOS handlers. >=20 > Have you found that drivers can be reliably loaded in parallel > these days? I'm always waiting for timeouts on four card readers > and two optical drives, so that would be a big win for me. IIRC, > nothing can happen in parallel during boot because the scheduler > is initialized very late in the process. I'm not a device driver > person, but I imagine there might be other assumptions that might > get in the way as well. Loading isn't the problem. The timeouts that you are waiting for are = part of the probe/attach sequence. And that's strictly serialized... Warner=