arm64: enable PREEMPT_LAZY

[PATCH 0/1] arm64: enable PREEMPT_LAZY

Posted by Valentin Schneider 11 months, 1 week ago

Hey folks,

This is a resubmission of Mark's patch [1]. I didn't end up changing anything
other than fluffing up the changelog.

I ran this under an arm64 VM, added some trace_printk's and checked that
sched_switch's between runnable hackbench threads would occurr in the right
conditions:
o with TIF_NEED_RESCHED_LAZY set
  o at the tick
  o at do_notify_resume()
o with TIF_NEED_RESCHED set  

[1]: https://lore.kernel.org/linux-rt-users/Z2B5y3HiLuRHPfdv@J2N7QTR9R3.cambridge.arm.com/

Cheers,
Valentin

Mark Rutland (1):
  arm64: enable PREEMPT_LAZY

 arch/arm64/Kconfig                   |  1 +
 arch/arm64/include/asm/thread_info.h | 16 +++++++++-------
 arch/arm64/kernel/entry-common.c     |  2 +-
 3 files changed, 11 insertions(+), 8 deletions(-)

--
2.43.0

Re: [PATCH 0/1] arm64: enable PREEMPT_LAZY

Posted by Will Deacon 9 months, 1 week ago

On Wed, 05 Mar 2025 11:49:24 +0100, Valentin Schneider wrote:
> Hey folks,
> 
> This is a resubmission of Mark's patch [1]. I didn't end up changing anything
> other than fluffing up the changelog.
> 
> I ran this under an arm64 VM, added some trace_printk's and checked that
> sched_switch's between runnable hackbench threads would occurr in the right
> conditions:
> o with TIF_NEED_RESCHED_LAZY set
>   o at the tick
>   o at do_notify_resume()
> o with TIF_NEED_RESCHED set
> 
> [...]

Applied to arm64 (for-next/entry), thanks!

[1/1] arm64: enable PREEMPT_LAZY
      https://git.kernel.org/arm64/c/c8597e2dd8b6

Cheers,
-- 
Will

https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev

Re: [PATCH 0/1] arm64: enable PREEMPT_LAZY

Posted by Petr Tesarik 9 months, 1 week ago

On Tue, 29 Apr 2025 21:27:52 +0100
Will Deacon <will@kernel.org> wrote:

> On Wed, 05 Mar 2025 11:49:24 +0100, Valentin Schneider wrote:
> > Hey folks,
> > 
> > This is a resubmission of Mark's patch [1]. I didn't end up changing anything
> > other than fluffing up the changelog.
> > 
> > I ran this under an arm64 VM, added some trace_printk's and checked that
> > sched_switch's between runnable hackbench threads would occurr in the right
> > conditions:
> > o with TIF_NEED_RESCHED_LAZY set
> >   o at the tick
> >   o at do_notify_resume()
> > o with TIF_NEED_RESCHED set
> > 
> > [...]  
> 
> Applied to arm64 (for-next/entry), thanks!
> 
> [1/1] arm64: enable PREEMPT_LAZY
>       https://git.kernel.org/arm64/c/c8597e2dd8b6

Great news. Thank you!

Petr T

Re: [PATCH 0/1] arm64: enable PREEMPT_LAZY

Posted by Phil Auld 11 months, 1 week ago

On Wed, Mar 05, 2025 at 11:49:24AM +0100 Valentin Schneider wrote:
> Hey folks,
> 
> This is a resubmission of Mark's patch [1]. I didn't end up changing anything
> other than fluffing up the changelog.
> 
> I ran this under an arm64 VM, added some trace_printk's and checked that
> sched_switch's between runnable hackbench threads would occurr in the right
> conditions:
> o with TIF_NEED_RESCHED_LAZY set
>   o at the tick
>   o at do_notify_resume()
> o with TIF_NEED_RESCHED set  
> 
> [1]: https://lore.kernel.org/linux-rt-users/Z2B5y3HiLuRHPfdv@J2N7QTR9R3.cambridge.arm.com/
>

Thanks!  I was looking for this the other day :) 


Cheers,
Phil

> Cheers,
> Valentin
> 
> Mark Rutland (1):
>   arm64: enable PREEMPT_LAZY
> 
>  arch/arm64/Kconfig                   |  1 +
>  arch/arm64/include/asm/thread_info.h | 16 +++++++++-------
>  arch/arm64/kernel/entry-common.c     |  2 +-
>  3 files changed, 11 insertions(+), 8 deletions(-)
> 
> --
> 2.43.0
> 

--