| Re: [ckrm-tech] [PATCH 4/13] BC: context handling [message #8528 is a reply to message #8527] |
Thu, 23 November 2006 08:53   |
Paul Menage
Messages: 642
Registered: September 2006
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Senior Member |
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On 11/23/06, Pavel Emelianov <xemul@openvz.org> wrote:
>
> We can do the following:
>
> if (tsk == current)
> /* fast way */
> tsk->exec_bc = bc;
> else
> /* slow way */
> stop_machine_run(...);
>
> What do you think?
How about having two pointers per task:
- exec_bc, which is the one used for charging
- real_bc, which is the task's actual beancounter
at the start of irq, do
current->exec_bc = &init_bc;
at the end of irq, do
current->exec_bc = current->real_bc;
When moving a task to a different bc do:
task->real_bc = new_bc;
atomic_cmpxchg(&task->exec_bc, old_bc, new_bc);
(with appropriate memory barriers). So if the task is in an irq with a
modified exec_bc pointer, we do nothing, otherwise we update exec_bc
to point to the new real_bc.
Paul
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