[Sugar-devel] Sugar-devel Digest, Vol 11, Issue 89 (SoaS performance/hard drive swapping)

[Bill Bogstad]

On Wed, Sep 16, 2009 at 7:56 PM, Douglas McClendon
<dmc at filteredperception.org> wrote:
> Bill Bogstad wrote:
>> [swapping on hard disk with SoaS
>>
>> Anybody want to code/script this up?
>
> does /etc/rc.d/init.d/livesys (search for swapon) in f11/soas not already do
> just that?

I just checked both F11 Live and SoaS Live ISOs.  You are absolutely
correct for both.
It checks for partitions marked as swap and then mounts all of them.
I even tested
it with the SoaS Live ISO under virtualization and it mounted the swap
partition as expected.
Current SoaS deployments can take advantage of this without requiring
any changes to students sticks.  If someone gets a chance, it would be
interesting to see how much performance changes on low memory systems
when you do this.

>> Or we could make a swap file on the flash stick (not in the Linux root
>> filesystem though, too many levels of indirection for good
>> performance).  This could be setup to only be turned on when the
>> physical memory in the machine is below a certain amount.
>
> With the wide variance in performance of usb drives (from rotating, to good
> flash, to old cheap slow flash), I think you might need more logic to get a
> good general purpose solution here.

The funny thing is that if livesys finds a file called swap.img on the
live media it uses that for swap  as well.  No attempts to check for
memory size.  Doesn't pay attention to the fact
that it may already be swapping to disk.  It just uses it.  Apparently
the original developers
of the livesys code decided to at least make it an option.  This could
be useful with
the XO-1.  You could throw a cheap SD card into those machines and use
it for swapping.
As software (invariably) bloats, this could extend the life of this machines.

Bill Bogstad