SD card unpartitioned space -- used for swap?

[C. Scott Ananian]

Assuming OLPC isn't using TRIM support on the SD cards, writes to the
swap space are indistinguishable from writes to any other space on the
card.  That means that writes to the swap "partition" could
potentially corrupt other data on the card, especially if it occurs
less than 30s before removal of power (or whatever that evil keepout
time is).

>From my recent experience, I wouldn't be too worried about swap space
"wearing out" the SD card, as we used to -- but that's not to say it's
100% safe, all reads and writes are risky to some degree.  We've seen
up to 60s delays on reads from flash as well, you might consider how
that might affect perceived performance.

FWIW, litl also uses a no-swap-space linux setup.  We haven't actually
had any problems with it; bugs I thought I could pin on
low-memory/no-swap issues turned out to actually be bugs in the Atom
page table hardware (!) which were exacerbated when lots of page table
operations were done -- in our case, GPU-heavy tasks triggered the bug
just as well.  Our superstitions about OLPC's no-swap configuration
may well prove to be similarly unfounded.
  --scott

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