On 22/09/2022 11:52, Catalin Marinas wrote:
On Thu, Sep 22, 2022 at 10:34:45AM +0100, James Clark wrote:
On 21/09/2022 16:08, Catalin Marinas wrote:
- Always on CONFIG_PID_IN_CONTEXTIDR (we might as well remove the Kconfig entry). This would write the root pid namespace value (task_pid_nr()).
If we're not worried about the overhead after all, this would be the easiest solution. And then SPE or Coresight already decide whether they want to use the value or not, so no further changes are needed.
From Leo's patch there is a table that shows a 1% overhead with it enabled permanently, and I've heard a figure like that mentioned before. So I could also resurrect that patch to use static keys? Although it's a bit more complicated, that would be my preference. And then we can have that mode always on.
I don't think we should bother with static keys, just always enable it but try to reduce/group the ISBs from all the functions called on the __switch_to() path. We may actually get a speed-up.
Ok thanks I will take a look at this