CPU Utilization higher with 13.12 drivers

[JimF]

I just found that the CPU utilization of Core_17 (P8900) is higher when using the 13.12 drivers as compared to the 13.9 drivers (Win7 64-bit). For example the CPU utilization with the 13.9 drivers runs about 1% or less as measured by Task Manager (that is, less than about 10% per virtual core of an Ivy Bridge or Haswell machine). On the other hand, it runs about 9 to 10% with the 13.12 drivers (that is, about 70 to 80% of a virtual core). At first, I thought this was just the high CPU utilization during the initial start-up phase of a work unit, but it persisted.

I have two HD 7870s on the Ivy Bridge, and two HD 7790s on the Haswell; maybe different cards yield different results? I don't see any PPD difference yet, but it is still early for that.

[3D_Now!!]

I was just about to post a comment similar to this. I have a haswell 4670k and 2 HD7790's on windows 8.1 (64 bit) with the new 13.12 driver (WHQL). CPU utilisation is up to ~10% per core as per JimF's comment above, whereas it used to sit around 1%. I only upgraded the driver due to the frame pacing improvements on games. Is this an OpenCL issue?

[bruce]

Is this an OpenCL issue?

Perhaps, but since OpenCL is packaged as part of the drivers, it's safer to simply say it's a driver issue. There are certain trade-offs that are made by those who write drivers and those decisions influence how much CPU is used. If the fundamental requirement is to maximize video performance it's not unreasonable to use more CPU processing if it allows your display to update more quickly.

It the past, ATI tech support gave us information which allowed experts to tune internal driver settings depending on whether we wanted minimum CPU utilization or maximum GPU performance. Unfortunately I have not seen a tuning guide for current generation drivers and I doubt the old information would be still useful.

[JimF]

If anything, the 13.9 drivers seem to be slightly faster; closer to 39K PPD on my 7790s, rather than 38K PPD with the 13.12 drivers, though with numbers that close it could be just the work units themselves. However, I am not a gamer, and use the internal Intel graphics adapter for my display anyway, so I can just choose the drivers that work best for Folding.