Re: Paralell startup
Wed, 20 Oct 2004 14:09:10 -0400
Date: Wed, 20 Oct 2004 10:53:17 -0400
From: Arjan van de Ven <arjanv@xxxxxxxxxx>
Subject: Re: Paralell startup
On Tue, 2004-10-19 at 12:10, Kyrre Ness Sjobak wrote:
problem with parallel startup is that it *ALSO* increases how much the
disk has to seek, which slows things down. For me it's not clear if
it's actually a real gain or just a placebo one.
I am hearing much good from the gentoo camp about paralell startup, and
how it brings down boot times to about 30 secounds. Is this possible to
do with fedora as well?
You are right ... just starting up everything that can possibly be
started up all at once makes no sense since it will undoubtedly add
overhead above and beyond the time for each to start separately.
There are some situations/landmarks that are independant of disk access
I would break things up into three phases of booting:
1) Hardware detection and configuration - pretty much everything has to
wait for this (and all the HAL/hotplug/udev stuff is looking really
2) Network connection - there are going to be many things that need to
wait for a network interface to be established but many others that
couldn't care less and could continue on loading up without waiting for
slow DHCP resolution or a bit long timeout before ifup failure (both
things catch me on a regular basis).
3) X server startup and presentation of GUI login - this could be
spawned quite early on while everything else keeps loading in the
background. Psychologically, many people believe that the boot is done
when they can interact with the machine. Windows uses this trick
extensively. While it looks like it has booted, try opening up an app
... it takes *ages* until it has truly finished loading everything in
Each of these milestones can "fork" off a parallel ordered branch of
startup scripts which may _seem_ to start up faster and avoid big pauses
when there is trouble. It shouldn't add too much complication to the
init. Each script just has to identify whether it needs networking to be
up or if it blocks X.
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