[linux-mm-cc] Compressed swapping to nand memory

[John Kielkopf]

One area where comcache has been a big help is on older Android phones
with limited memory.  Unfortunately even compcache is not able to
effectively deliver the amount of memory necessary for some of these
devices to run the more recent versions of Android well.
 

Because of this, I wondered if compcache ever looked in the direction of
compressed swapping to nand, specifically to SD.
 
 From what I
understand, for this to happen and perform well one would  need to:


 1) Buffer and remap pages being swapped out into segments that are
the size of the nand device's erase block to avoid the read/erase/write
penalty.
 
 2) Find a way to deal with the fragmentation of the
page file that will happen with use eventually leaving no free erase block
sized segments available. (use an over-sized page file?)
 
 3)
Deal with wear leveling to avoid premature failure of the nand (if using
SD, or other devices that support wear leveling, this may be
unnecessary.)
  
 Adding compression to swap of all types,
not just ram, seems a logical direction, yet the only project that appears
to have ever tried to deal with it** seems to have been abandoned when
Numonyx spun off of intel in 2008.
 
 Is this a direction
compcache has ever experimented with?  Is there a reason that
interest in compressed swapping to nand is so low when it appears to hold
so much promise for embedded devices?
 
 ** http://www.celinux.org/elc08_presentations/belyakov_elc2008_compressed_swap_final_doc.pdf
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