lkml.org 
[lkml]   [2016]   [Feb]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH V2 3/6] stm class: provision for statically assigned masterIDs
From
On 8 February 2016 at 10:44, Al Grant <Al.Grant@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.

\
 
 \ /
  Last update: 2016-02-09 18:21    [W:0.097 / U:2.216 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site