On 03/06/2014 07:25 AM, David Lang wrote:
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
Using vdso reduces the cost of system call significantly, but as Peter
pointed out a thread can not really rely upon the number it will get back.
--
Khalid
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