Re: [PATCH 2/2] drm/i915: Handle inaccurate time conversion issues

Chris Wilson
2014-11-28T11:08:51Z

On Fri, Nov 28, 2014 at 10:29:55AM +0100, Daniel Vetter wrote:
> So apparently jiffies<->nsec<->ktime isn't accurate or something. At
> elast if we timeout there's occasionally still a few hundred us left
> (in a 2 second timeout).
>
> Stuff I've tried and thrown out again:
> - Sampling the before timestamp before jiffies. Doesn't improve test
> path rate at all.
> - Using jiffies. Way to inaccurate, which means way too much drift
> with signals plus automatic ioctl restarting in userspace. In
> hindsight we should have used an absolute timeout, but hey we need
> something for v3 of the i915 gem wait interfaces ;-)

I am still trying to get my head around an ioctl that only works in
jiffie intervals where the jiffie is too inaccurate.
-Chris

--
Chris Wilson, Intel Open Source Technology Centre