[PATCH v5] um: Enable preemption in UML

[Anton Ivanov]

On 22/09/2023 10:04, Johannes Berg wrote:
> On Fri, 2023-09-22 at 10:43 +0200, Johannes Berg wrote:
>>>
>>> I think this has pretty much always been wrong, just now we actually
>>> notice it?
>>>
>>> Basically, when we create a new thread (really just mm I think), we say
>>> the first thing that has to run there is fork_handler(), which
>>> initialises things the first time around. This calls force_flush_all()
>>>
> 
> So I thought we could perhaps just force_flush_all() the new mm in
> init_new_context(), but that segfaults userspace immediately.
>

Been there done that.

> So I need to fully understand first (again?) why we even need
> force_flush_all() at this spot, but probably not today.
No idea, but it does not seem to work without it. This is actually
the biggest performance bugbear in UML. If this is fixed, the 
performance will go reasonably close to native.

> 
> johannes
> 
> _______________________________________________
> linux-um mailing list
> linux-um at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-um
> 

-- 
Anton R. Ivanov
Cambridgegreys Limited. Registered in England. Company Number 10273661
https://www.cambridgegreys.com/