Originally Posted by
sturmflut
There aren't that many uses for GPGPU processing inside the kernel besides cryptography. The cards use a separate memory range and the time required to setup a task on the GPU is pretty high. Most kernel calls do not operate on large portions of data, they just pass them around between user-space programs and peripherial devices, so the processing power of a GPU cannot benefit the task. In most cases a task will probably even take longer, because copying the data to the GPU, starting the GPGPU task and copying the data back heavily increases the latency.
This is the exact same reason why it doesn't currently make sense to use GPGPU computing in most standard applications, like Microsoft Office or a Web Browser: The workloads are so small that a standard CPU can deliver the result faster than a GPU round-trip would take. And most CPUs nowadays have multiple cores anyways. Maybe the situation improves once CPU and GPU are combined into a single devices with a common, flat memory layout, but the GPU is still no good for small workloads.
Probably that's why they picked file system cryptography, but newer CPUs come with AES accelerators, and currently available AES-NI units already peak out at up to two gigabytes per second. That's enough to saturate multiple S-ATA links, and AES-NI comes with no additional memory copies, setup times etc., while completely freeing the CPU for other tasks.
