Parallel Booting

[darrell pfeifer]

On 7/6/07, Alan Cox <alan at redhat.com> wrote:
> On Fri, Jul 06, 2007 at 04:55:47PM -0400, Colin Walters wrote:
> > Possibly, but I think the biggest speedup by far is the disk
> > caching/reorganization that both Windows and OS X do:
> > http://www.kernelthread.com/mac/apme/optimizations/
> >
> > At this rate though, we might all be using solid state drives before the
> > kernel developers stop pointing at userspace as the problem and
> > implement it for Linux.
>
> We already lay stuff out very carefully and precache. Unfortunately most
> of the mess *is* userspace and some of the userspace authors are in
> complete denial. Just profile the number of file opens of different files
> done in a gnome startup and when you've finished laughing you can weep.
>
> Years ago I sent the gnome team a library that could load and linearlly
> map the entire theme in about 3 syscalls coming out nicely on disk. They
> never used it.
>
> That isn't to say the kernel is perfect and there is a ton of optimising
> work still going on, different scheduling algorithms and the like but
> most of the slowness is from user space - some from tools, some from
> combinations of tools and kernel (eg linker and paging patterns) and a lot
> of it from sheer stupid clueless design of applications and especially
> of GUI libraries.
>

Speaking from my many days as a performance analyst, Pfeifer's first
rule of performance says "The only good I/O is one you don't do".

I'll second Alan here. The OS can mitigate the effects of I/O but
userspace has the onus to be reasonable.

darrell