On 8 February 2016 at 10:44, Al Grant <al.gr...@arm.com> wrote: >> Mike did write "master IDs are hardwired to individual cores and core >> security >> states", which make assignment for one platform very static. >> On the flip side those will change from one system to another. > > It depends on your perspective. From the perspective of a userspace > process not pinned to a core, the master id will appear to vary > dynamically and unpredictably as the thread migrates from one > core to another. (That's actually useful if the decoder wants to know > where the thread is running at any given point, as it can find that out > for free, without the need to track migration events.)
Right, that's the expected (and desired) behaviour. > > On the other hand if you are pinned (e.g. you're the kernel on a > particular core, or you're a per-core worker thread in some thread > pooling system) then you have a fixed master id, and then you can > have one instance per core all using the same range of channel > numbers, with the master id indicating the core - this saves on > channel space compared to having to give each core its own > range of channel space. >From an STM core and driver point of view channel mapping works the same way - pinning of tasks is a kernel artefact. The problem of representing masterIDs in the STM core for an architecture with HW assigned masterIDs is still unresolved. > > Al > IMPORTANT NOTICE: The contents of this email and any attachments are > confidential and may also be privileged. If you are not the intended > recipient, please notify the sender immediately and do not disclose the > contents to any other person, use it for any purpose, or store or copy the > information in any medium. Thank you. -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
