Hi all,
On 2020-12-08 20:02, Joel Fernandes wrote:
On Fri, Sep 11, 2020 at 4:58 AM Sergey Senozhatsky
<sergey.senozhatsky@xxxxxxxxx> wrote:
My apologies for the slow reply.
On (20/08/17 13:25), Marc Zyngier wrote:
>
> It really isn't the same thing at all. You are exposing PV spinlocks,
> while Sergey exposes preemption to vcpus.
>
Correct, we see vcpu preemption as a "fundamental" feature, with
consequences that affect scheduling, which is a core feature :)
Marc, is there anything in particular that you dislike about this RFC
patch set? Joel has some ideas, which we may discuss offline if that
works for you.
Hi Marc, Sergey, Just checking what is the latest on this series?
I was planning to give it a go, but obviously got sidetracked. :-(
About the idea me and Sergey discussed, at a high level we discussed
being able to share information similar to "Is the vCPU preempted?"
using a more arch-independent infrastructure. I do not believe this
needs to be arch-specific. Maybe the speciifc mechanism about how to
share a page of information needs to be arch-specific, but the actual
information shared need not be.
We already have some information sharing in the form of steal time
accounting, and I believe this "vcpu preempted" falls in the same
bucket. It looks like we could implement the feature as an extension
of the steal-time accounting, as the two concepts are linked
(one describes the accumulation of non-running time, the other is
instantaneous).
This could open the door to sharing
more such information in an arch-independent way (for example, if the
scheduler needs to know other information such as the capacity of the
CPU that the vCPU is on).
Quentin and I have discussed potential ways of improving guest
scheduling
on terminally broken systems (otherwise known as big-little), in the
form of a capacity request from the guest to the host. I'm not really
keen on the host exposing its own capacity, as that doesn't tell the
host what the guest actually needs.
Thanks,
M.
--
Jazz is not dead. It just smells funny...
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