Opportunity for speedup

david at lang.hm david at lang.hm
Thu Feb 19 15:00:10 EST 2009

On Thu, 19 Feb 2009, Mitch Bradley wrote:

> david at lang.hm wrote:
>> if you have the diff of the images, do you need to read from the 
>> framebuffer at all? since you know what you put there, and know what you 
>> want to change, can't you just write your changed information to the right 
>> place?
> The framebuffer in this case is serving as persistent shared memory, thus 
> avoiding the extra complexity of a client/server architecture to maintain the 
> sequencing state.
> The extremely-tiny (4K - 1 memory page) client program initially reads the 
> first frame into the on-screen framebuf and the delta set into off-screen 
> framebuffer memory.  On subsequent invocations, the client copies another 
> delta into the on-screen framebuf.
> If it is statically linked and uses only direct syscalls, the exec() overhead 
> is minimal - no shell process instantiation, no script startup, no ld.so 
> invocations, no mapping in shared libraries, no relocation.

right, but why read the current framebuffer? you don't touch most of it, 
you aren't going to do anything different based on what's there (you are 
just going to overlay your new info there) so all you really need to do is 
to write the parts tha need to change.

David Lang

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