Le 10/02/2021 à 03:00, Nicholas Piggin a écrit :
Excerpts from Christophe Leroy's message of February 10, 2021 3:03 am:
Le 09/02/2021 à 15:31, David Laight a écrit :
From: Segher Boessenkool
Sent: 09 February 2021 13:51
On Tue, Feb 09, 2021 at 12:36:20PM +1000, Nicholas Piggin wrote:
Excerpts from Christophe Leroy's message of February 10, 2021 3:03 am:
>
>
> Le 09/02/2021 à 15:31, David Laight a écrit :
>> From: Segher Boessenkool
>>> Sent: 09 February 2021 13:51
>>>
>>> On Tue, Feb 09, 2021 at 12:36:20PM +1000, Nicholas Piggin wrote:
What if you did this?
>>>
From: Christophe Leroy
> Sent: 09 February 2021 17:04
>
> Le 09/02/2021 à 15:31, David Laight a écrit :
> > From: Segher Boessenkool
> >> Sent: 09 February 2021 13:51
> >>
> >> On Tue, Feb 09, 2021 at 12:36:20PM +1000, Nicholas Piggin wrote:
> >>> What if you did this?
> >>
> >>> +static inline
Le 09/02/2021 à 15:31, David Laight a écrit :
From: Segher Boessenkool
Sent: 09 February 2021 13:51
On Tue, Feb 09, 2021 at 12:36:20PM +1000, Nicholas Piggin wrote:
What if you did this?
+static inline struct task_struct *get_current(void)
+{
+ register struct task_struct *task
From: Segher Boessenkool
> Sent: 09 February 2021 13:51
>
> On Tue, Feb 09, 2021 at 12:36:20PM +1000, Nicholas Piggin wrote:
> > What if you did this?
>
> > +static inline struct task_struct *get_current(void)
> > +{
> > + register struct task_struct *task asm ("r2");
> > +
> > + return
On Tue, Feb 09, 2021 at 12:36:20PM +1000, Nicholas Piggin wrote:
> What if you did this?
> +static inline struct task_struct *get_current(void)
> +{
> + register struct task_struct *task asm ("r2");
> +
> + return task;
> +}
Local register asm variables are *only* guaranteed to live in
Excerpts from Christophe Leroy's message of February 9, 2021 1:10 am:
> By saving the pointer pointing to thread_info.flags, gcc copies r2
> in a non-volatile register.
>
> We know 'current' doesn't change, so avoid that intermediaite pointer.
>
> Reduces null_syscall benchmark by 2 cycles (322
By saving the pointer pointing to thread_info.flags, gcc copies r2
in a non-volatile register.
We know 'current' doesn't change, so avoid that intermediaite pointer.
Reduces null_syscall benchmark by 2 cycles (322 => 320 cycles)
On PPC64, gcc seems to know that 'current' is not changing, and it
