Date: Thu, 12 Jul 2001 10:32:32 -0700 From: Terry Lambert <tlambert2@mindspring.com> To: obrien@FreeBSD.ORG, Bill Moran <wmoran@iowna.com>, freebsd-hackers@FreeBSD.ORG Subject: Re: FreeBSD Mall now BSDCentral Message-ID: <3B4DDF30.9CEAAAFB@mindspring.com> References: <20010706144935.A61843@xor.obsecurity.org> <3B4650D0.97F10B83@bellatlantic.net> <20010707002340.B16071@widomaker.com> <20010707004731V.jkh@osd.bsdi.com> <3B49F8D5.2C9BFA73@mindspring.com> <3B4A0124.26025FB5@iowna.com> <3B4A1423.E8E365E@mindspring.com> <20010709144801.A38630@dragon.nuxi.com> <3B4B26FE.6660FE5C@mindspring.com> <20010710091352.F48544@dragon.nuxi.com> <3B4B3A58.A6CFC592@mindspring.com>
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Terry Lambert wrote: > > David O'Brien wrote: > > There you go Terry, async mounts for installs. > > Thanks. > > This does not appear to work on upgrades for things > like /usr/ports. > > Now I will have to go find out why; how annoying: yet > more work. OK, I was right. The damn thing is not mounting async. There are a couple of reasons for this, when doing an upgrade: 1) Soft Updates enabled on a root partition. This comes back to the old "you can't turn SU on or off, except via tunefs". So even if you boot via CDROM, it's too late, if the CDROM kernel supports SU, since it's already on, and you can't substitute an async mount. Soft Updates are OK for a moderate amount of file replacement activity, but wholesale work is better done with async mounts. So what's needed is a way for async to take precedence (by flushing all pending updates, and updating the mount type). So the new default of "SU on" actually will interfere with upgrades (we do this from release snapshots I have built all the time, and we do it to recover lab and engineering machines to a known good state, before applying the most recent local changes). 2) Most of my upgrades are over a network, not booting off of CDROM. This means that it's not running as "init", so David's if() test he quoted me failed to attempt to activate async mounts; we don't have the option on a machine with a serial console and no floppy or CDROM to be able to select network booting, even though on some of the machines, there are Intel Netboot capable FXP cards. 3) The default in 4.3-RELEASE is to have the IDE write caching off. This is probably the biggest barrier to fast install/upgrade. It's not really possible to get around this on initial install, but on many of the machines, where we are doing the upgrade over an NFS mount with a copy of the sysinstall from the floppy image from the CDROM, (why isn't this duplicated on the CDROM anywhwere?) it's possible to turn on the write caching at boot time, and do an upgrade (NOT an install!) with the write caching enabled. The async mount still does not take place, because of the soft updates. NB: Yes, I'm aware this has been changed in the source tree, but it is not available on and CDROM distributions currently available. 4) I'm pretty sure that during a regular install, the default of newfs'ing with soft updates enabled is now _also_ preventing the use of true async mounts; again, for the most part, with only new file data, this is pretty fast, but you are once again up the creek without a paddle when it comes to installing the ports collection. So that's the status: for new installs, the complaint holds true for all upgrade cases, and the default install case for things with bad locality of reference (like ports). Hope this clarifies things. -- Terry To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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