Refractions and Volume Scattering...ridiculously long render times!

I have the following scene where a light ray is being scattered behind a glass. The whole scene renders pretty fast, tiles on non-glass materials only takes a few minutes to finish. However when it comes to rendering the glass it becomes super slow, tiles been stuck there for the majority of 5 hours now (screenshot below).

Using 2000 samples, indirect clamp to 4 and max bounces at 6. Refractions without the volume scattering also renders pretty quick.

CPU: 4770k at 4.0GHz
GPU: 780Ti 3GB

Is this a known bug? Are there any tips or workarounds to speed up the render times when it comes to refractions, without sacrificing much quality? Thanks in advance.

It’s a slow effect viewed indirectly through slow effect. It’s gonna be slow. Why are you using scattering for the contents of a glass anyway? The SSS shader is a lot faster and should work fine.

Seems that I didn’t explain well enough. The glass itself is just a pure Glass shader, no volume or anything. Behind it (In front of the door) is a cube with Volume scatter + absorb shaders in order to scatter the light coming through the door. The glass itself is not even inside this volume domain and the volume is set to 0 bounces so I’m a bit puzzled why it’s taking too long to render.

w/o scene it hard to tell. Did you use volume for cake and object inside glass? maybe you by occasion use input plugs in Absorb/scattering that force Cycles to very slow variable density algorithm?

Are you using the Branched Path integrator for this? I ask because that integrator I find to be quite slow with complex shading and lighting effects to the point where you actually lose a lot of time compared to simply using Progressive (despite playing with the sampling values).