Shared memory transport for X (was Re: Security question?)
idr at us.ibm.com
Wed Nov 3 19:24:31 PST 2004
Adam Jackson wrote:
> SGI and DEC too. And internal to Xlib, AFAIK, still using the PF_UNIX socket
> for synchronization.
> Precision Insight did some research into adding this to XFree86 in the early
> 4.0 days, but it was decided that it wasn't worth the added complexity since
> shared memory transport only really helps when the graphics subsystem is much
> more powerful than the CPU. The original paper fell off the net, but I
> rescued it from the wayback machine:
> It would be interesting to see if the results in this paper can be improved
> upon by using linux futexes rather than the Unix socket for synchronization.
> The implementation referred to in this paper is still available on a branch
> of the DRI xc tree, if anyone feels like some archaeology.
The performance improvement might also be a lot larger for hardware
accelerated indirect rendering. Typical X requests don't have a lot of
data, but when you start throwing large vertex arrays and textures into
the mix, things change.
Using futexes is a good idea, BTW.
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