flat_mem: thoughts on swap

diff --git a/Kernel/flat_mem.c b/Kernel/flat_mem.c
index 3c8616a..be5dbb2 100644 (file)
--- a/Kernel/flat_mem.c
+++ b/Kernel/flat_mem.c
@@ -24,6 +24,23 @@
  *             Pinning. This is actually quite hairy because we need to know
  *             that the address we are pinning has *no* users in any list.
  *             That will require better data structures for va management.
+ *
+ *     SWAPPING:
+ *             Two options
+ *             - we swap out processes (remembering the outgoing process
+ *             might not be identity mapped) but we then need to implement
+ *             a hole list for swap, and coalescing and the like
+ *             - we have a memblk entry for each page of RAM or swap and
+ *             we keep track of whether the 'page' is in RAM or swap. That
+ *             lets us do partial swap outs, swap out non identity mapped
+ *             pages first and try other things of that kind. At the
+ *             moment any memblk has a pa and va and we fast_swap_block
+ *             when we need too. Disk swapping would push them out to
+ *             the end part of the array that didn't exist in RAM but isn't
+ *             quite the same as 'exchange' isn't a disk function. Swap in
+ *             would magically happen as part of vmmu_setcontext, the
+ *             array offset tells us where in swap and we don't have to
+ *             coalesce.
  */
 
 #include "kernel.h"