On 1999/Oct/06, Andreas Beck wrote:
> > screen blinking a lot, I think. Anyway, there is another bigger problem,
> > IMO, that switching to kernel mode, copying data structures, and returning
> > back into user mode, may be too much time, and maybe when the ioctl returns,
> > you haven't enough time to copy your buffer.
>
> No. That shouldn't matter much. I once measured a full ioctl round trip on
> my old 486 to take 600 cycles. Given even that machine (486/66), this gives
> an extra delay of about 10 microseconds. Shouldn't be the crucial point.
If you are drawing objects with little polygons (i.e. a torus with
many polygon resolution), where each polygon can take 300 cycles or less,
it's very crucial, I think.
In fact, in 2D accel, I only draw hlines by hardware when they are
more than 100 pixels in length, because if they are shorter, drawing by
hardware is mucho more slow (because of the ioctl call?).
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