>> The right way to solve this is to make the Linux kernel contain the necessary >> heuristics to identify which tasks and thus cores need this to improve efficiency >> and then apply it automatically. >> >> Putting it in userspace is making a human do a machines job which isn't >> sustainable. >> >> By putting the heuristics in kernelspace Linux will improve performance also on >> workloads the human operator didn't think of as the machine will detect them from >> statictical or other behaviour patterns. > >In order to put the heuristics into kernelspace Linux, I think it >necessary to consider the following two points. > >1) Which cores are tied with the process? >This is different from the core on which the process can run. It >probably need to combine some CPU resource limit to avoid affecting >non-target processes. > >2) How to derive the value to set in the register? >It is necessary to verify whether an appropriate set value can be >derived using statistical information, etc. In addition, to prevent >the cost of automatic derivation from exceeding the value that would >be improved by it. > >I don't have a prospect for resolving these issues yet. I will >continue these considerations. Another approach would be to make the set of prefetch settings a task attribute. Then set them in the context switch code when the process is about to run on a CPU. But that assumes you can cheaply change the attributes. If doing so requires multiple MSR writes (on x86) it might be a non-starter. -Tony
