speeding up disk-based laptop by moving /usr to flash?

[brendan-j2ZBMMpYpO5eoWH0uzbU5w at public.gmane.org (Brendan Kidwell)]

On Wed, Dec 2, 2009 at 7:51 AM, Jerry Feldman <gaf-mNDKBlG2WHs at public.gmane.org> wrote:

> I don't think that would affect performance, and may even hurt
> performance. Remember that when Linux loads a program or a shared
> library, the location of that program or shared object effectively
> becomes part of swap. The program and its dependent shared libraries are
> mapped into memory, but only loaded into pages when needed.
>

I'm not convinced that it wouldn't improve performance. Consider starting up
OpenOffice.org (everyone's favorite gigantic application). A huge pile of
executables and SOs get memory mapped and lots and lots of pages in those
get randomly read and executed. On a filesystem that has a very low seek
time, all things being equal, it should perform better than a typical disk,
and streaming throughput would be of secondary concern I think. But all
things are equal only in high school physics problems.

The only way to really answer the question is to backup the whole system and
start reconfiguring and testing it.

Tom's suggestion of ZFS's demand-sensitive selective striping or some more
generic solution involving a Linux filesystem seems attractive as well. I'd
love it if I could find a good Linux based "ReadyBoost"-like flash-aware
cache module.

Lifehacker actually suggests mounting /dev/your-flash-memory as a secondary
swap device. I don't see how that'll do any good unless you have far too
little RAM. Doesn't swap get cleared whenever you shut down, so you have no
accumulated effect of keeping often-used objects in cache? And don't memory
mapped files like executables NEVER get loaded into swap, since in this case
the RAM is just shadowing sectors of storage?

What I would do is to look at possibly replacing the X41 since prices
> are now very low. Most new laptops today are built for Windows 7 which
> requires more memory so those laptops have more memory builtin.
>

At this point I don't think any replacement I'd be happy with would be in my
price range. And also, for reference, my motherboard is apparently already
maxed out with 1.5GB of RAM.


> But, first, analyze your boot time by looking at the time each step takes.
>

Thanks. That's a very important point and I already had that as a todo item
in my mind now that I've decided I'm not replacing the whole computer.