On 2020-08-17 13:03, yezengruan wrote:
On 2020/8/17 10:03, Sergey Senozhatsky wrote:
On (20/07/21 13:17), Sergey Senozhatsky wrote:
Hello,
RFC
We noticed that in a number of cases when we wake_up_process()
on arm64 guest we end up enqueuing that task on a preempted VCPU. The
culprit
appears to be the fact that arm64 guests are not aware of VCPU
preemption
as such, so when sched picks up an idle VCPU it always assumes that
VCPU
is available:
wake_up_process()
try_to_wake_up()
select_task_rq_fair()
available_idle_cpu()
vcpu_is_preempted() // return false;
Which is, obviously, not the case.
This RFC patch set adds a simple vcpu_is_preempted() implementation
so
that scheduler can make better decisions when it search for the idle
(v)CPU.
Hi,
A gentle ping.
-ss
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.
Hi Sergey,
I have a set of patches similar to yours.
https://lore.kernel.org/lkml/20191226135833.1052-1-yezengruan@xxxxxxxxxx/
It really isn't the same thing at all. You are exposing PV spinlocks,
while Sergey exposes preemption to vcpus. The former is a massive,
and probably unnecessary superset of the later, which only impacts
the scheduler (it doesn't change the way locks are implemented).
You really shouldn't conflate the two (which you have done in your
series).
M.
--
Jazz is not dead. It just smells funny...
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