Opportunity for speedup

Mitch Bradley wmb at laptop.org
Thu Feb 19 16:49:50 EST 2009

david at lang.hm wrote:
> d) compile the delta set into the client program.

That works, but

1) It requires more work from the VM system on each invocation of the 
client program, which is now 1.x MB instead of 4K.
2) If a deployment wants to change the image set, it needs a compiler 
toolchain instead of a (small) delta-encoding program.

Speed-wise, (d) might be a wash, or perhaps even a slight win.  It 
depends on how efficient the VM system is, and the effectiveness of the 
filesystem buffer cache at preventing re-reads of the client process 
image (paging directly from JFFS2 is not possible).

The framebuffer hack avoids numerous assumptions about the effectiveness 
of clever but complex subsystems (e.g. the VM system, the filesystem 
buffer cache, the shared library mechanisms, zlib, JFFS2 compression, ...).

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