Re: [RFC] [PATCH] Pre-emption control for userspace

[David Lang]

On Thu, 6 Mar 2014, Kevin Easton wrote:

> On Tue, Mar 04, 2014 at 04:51:15PM -0800, Andi Kleen wrote:
> > Anything else?
>
> If it was possible to make the time remaining in the current timeslice
> available to userspace through the vdso, the thread could do something like:
>
> if (sys_timeleft() < CRITICAL_SECTION_SIZE)
>    yield();
> lock();
>
> to avoid running out of timeslice in the middle of the critical section.

but won't the system call result in context switches? According to Kevin, even a 
context switch to another thread and back immediatly is bad enough to need to be 
avoided, so replacing that with the context switch to the kernel and back isn't 
a subtantial win.

David Lang
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