Re: [PATCH v2 11/11] mm,sched: conditionally skip lazy TLB mm refcounting

[Rik van Riel]

On Tue, 2018-07-31 at 07:29 -0700, Andy Lutomirski wrote:
> > On Jul 31, 2018, at 2:12 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> > wrote:
> > 
> > > On Mon, Jul 30, 2018 at 09:05:55PM -0400, Rik van Riel wrote:
> > > > On Mon, 2018-07-30 at 18:26 +0200, Peter Zijlstra wrote:
> > > > 
> > > > So for ARCH_NO_ACTIVE_MM we never touch ->active_mm and
> > > > therefore
> > > > ->active_mm == ->mm.
> > > 
> > > Close, but not true for kernel threads, which have a 
> > > NULL ->mm, but a non-null ->active_mm that gets passed
> > > to enter_lazy_tlb().
> > 
> > I'm confused on the need for this. We mark the CPU lazy, why do we
> > still
> > care about this?
> 
> I have considered renaming enter_lazy_tlb() to something like
> lazy_switch_to_kernel_mm() (or an irqs_off variant) and making it
> take no parameters or maybe just task pointer parameters. 

Of all the architectures, only Alpha uses the "mm"
parameter to enter_lazy_tlb.

It uses it to store the pgd address of the current
active_mm context into the thread info of the next
task.

If it can get that from a per CPU variable, we can
get rid of the mm parameter to enter_lazy_tlb.

-- 
All Rights Reversed.

Attachment: signature.asc
Description: This is a digitally signed message part