Date: Sat, 11 Jun 2011 17:07:24 -0600 From: Warner Losh <imp@bsdimp.com> To: David Schultz <das@FreeBSD.ORG> Cc: mdf@FreeBSD.ORG, Adrian Chadd <adrian@FreeBSD.ORG>, freebsd-arch@FreeBSD.ORG Subject: Re: [RFC] shipping kernels with default modules? Message-ID: <D721F18A-6ACB-4AB5-83FD-DB23D62BF5D3@bsdimp.com> In-Reply-To: <20110611204326.GA51320@zim.MIT.EDU> References: <BANLkTin2AwKRT7N6HWqBctJcT72_mR=Otg@mail.gmail.com> <20110611171834.GA38142@zim.MIT.EDU> <BANLkTik=z-fb1sDwh0dr4hRWmdhLMWiKdw@mail.gmail.com> <20110611204326.GA51320@zim.MIT.EDU>
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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 <das@freebsd.org> = 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=
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