Wrote two articles recently for Anandtech. “A deep dive on HSA” was a theoretical look at HSA and related technologies such as HSAIL, hUMA and hQ as well as the programming tools infrastructure. Next I wrote a bit about the floating point performance (both on CPU and GPU) of recent Intel and AMD chips including Kaveri.
Do check them out and let me know what you think 🙂
HSA Foundation finally released the Programmer’s Reference Manual for HSA IL (HSAIL). So what is HSAIL and why should you care about it? Well AMD and HSA Foundation have been talking about Heterogeneous System Architecture or HSA. HSAIL is one of the building blocks of HSA. Salient features of HSAIL are:
- HSAIL is a portable low-level pseudo assembly language for heterogeneous systems. HSAIL is not intended to be the real instruction set architecture (ISA) of any hardware. Instead, the hardware vendor will provide a compiler that will convert HSAIL to the actual ISA. For example, AMD will provide a driver to compile HSAIL to future AMD APUs.
- A regular programmer will never need to read/write HSAIL. Instead, it is intended as a code generation target for high level compilers. For example, you may have a C++ AMP or some sort of a Python compiler that generates HSAIL and then the hardware vendor’s driver will compiler HSAIL to the hardware.
- HSAIL is a very cleanly designed language. Compiling HSAIL to native code should be very fast in most cases.
- HSAIL is a very flexible language. Any GPU implementing HSAIL will have very advanced capabilities, far beyond current standards such as OpenCL 1.2. For example, HSAIL allows GPU kernels to enqueue calls to further GPU kernels without CPU intervention. Function pointers (and hence C++ virtual functions) are supported.
HSA-enabled systems will implement unified memory space for both CPU and GPU. Combined with the flexible execution model defined by HSAIL, I am very excited by the prospects of HSA enabled products such as the Kaveri APU. I am working on a more detailed writeup about HSA and will post it soon.