Re: [PATCH 0/4] s390: Idle time accounting improvements

[Heiko Carstens <hca@linux.ibm.com>]

On Wed, May 13, 2026 at 04:01:25PM +0200, Heiko Carstens wrote:
> This series is on top of Frederic Weisbecker's idle cpu time accounting
> refactor series [1][2].
> 
> This is supposed to improve s390 idle time accounting, and brings it
> back to the state it was before arch_cpu_idle_time() was removed from
> s390 [3].
> 
> In result all cpu time accounting is done by the s390 architecture backend
> again, instead of having a mix of architecure specific and common code
> accounting (common code: idle, s390 architecture: everything else).

Thomas, Peter, Frederic, any objections to this series? The third patch
touches common code, so I'd like to get an ACK for that.

If there is agreement, this could go either via tip tree's timers/nohz branch
(series applies cleanly), or via s390, after the nohz branch has been merged
upstream.

[Full quote below for reference]

> Changes since RFC [4]:
> 
> - Split into more patches
> 
> - Fix various build errors for !CONFIG_NO_HZ_COMMON
> 
> - Get rid of private seqcount implementation and access seqcount from
>   kernel_cpustat directly from assembler code, as suggested by Frederic
>   Weisbecker
> 
> [1] https://lore.kernel.org/all/20260508131647.43868-1-frederic@kernel.org/
> [2] git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git timers/core-v4
> [3] commit be76ea614460 ("s390/idle: remove arch_cpu_idle_time() and corresponding code")
> [4] https://lore.kernel.org/all/20260225145146.1031705-1-hca@linux.ibm.com/
> 
> Heiko Carstens (4):
>   s390/timex: Move union tod_clock type to separate header
>   s390/irq/idle: Use stcke instead of stckf for time stamps
>   s390/idle: Provide arch specific kcpustat_field_idle()/kcpustat_field_iowait()
>   s390/idle: Remove idle time and count sysfs files
> 
>  arch/s390/include/asm/idle.h      |  14 ++--
>  arch/s390/include/asm/lowcore.h   |   4 +-
>  arch/s390/include/asm/timex.h     |  20 +----
>  arch/s390/include/asm/tod_types.h |  30 +++++++
>  arch/s390/include/asm/vtime.h     |   4 +-
>  arch/s390/kernel/asm-offsets.c    |   7 ++
>  arch/s390/kernel/entry.S          |  14 +++-
>  arch/s390/kernel/idle.c           | 129 +++++++++++++++++++++++-------
>  arch/s390/kernel/irq.c            |   7 +-
>  arch/s390/kernel/smp.c            |  33 +-------
>  arch/s390/kernel/vtime.c          |  55 +------------
>  drivers/s390/cio/qdio_main.c      |   2 +-
>  drivers/s390/cio/qdio_thinint.c   |   2 +-
>  include/linux/kernel_stat.h       |  27 +++++++
>  include/linux/vtime.h             |   6 ++
>  kernel/sched/cputime.c            |   4 +-
>  16 files changed, 203 insertions(+), 155 deletions(-)
>  create mode 100644 arch/s390/include/asm/tod_types.h
> 
> base-commit: e64ba052ce04e363ff76d3cb8bedc5f812188acb
> -- 
> 2.51.0
> 
>