[PATCH 0/8] Generic IRQ entry/exit support for powerpc
Samir M
samir at linux.ibm.com
Tue Nov 11 16:09:31 AEDT 2025
On 11/11/25 10:09 am, Samir M wrote:
> On 02/11/25 5:23 pm, Mukesh Kumar Chaurasiya wrote:
>> Adding support for the generic irq entry/exit handling for PowerPC. The
>> goal is to bring PowerPC in line with other architectures that already
>> use the common irq entry infrastructure, reducing duplicated code and
>> making it easier to share future changes in entry/exit paths.
>>
>> This is slightly tested of ppc64le and ppc32.
>>
>> The performance benchmarks from perf bench basic syscall are below:
>>
>> | Metric | W/O Generic Framework | With Generic Framework | Change |
>> | ---------- | --------------------- | ---------------------- | ------ |
>> | Total time | 0.939 [sec] | 0.938 [sec] | ~0% |
>> | usecs/op | 0.093900 | 0.093882 | ~0% |
>> | ops/sec | 1,06,49,615 | 1,06,51,725 | ~0% |
>>
>> Thats very close to performance earlier with arch specific handling.
>>
>> Tests done:
>> - Build and boot on ppc64le pseries.
>> - Build and boot on ppc64le powernv8 powernv9 powernv10.
>> - Build and boot on ppc32.
>> - Performance benchmark done with perf syscall basic on pseries.
>>
>> Changelog:
>>
>> RFC -> PATCH
>> - Fix for ppc32 spitting out kuap lock warnings.
>> - ppc64le powernv8 crash fix.
>> - Review comments incorporated from previous RFC.
>> RFC
>> https://lore.kernel.org/all/20250908210235.137300-2-mchauras@linux.ibm.com/
>>
>> Mukesh Kumar Chaurasiya (8):
>> powerpc: rename arch_irq_disabled_regs
>> powerpc: Prepare to build with generic entry/exit framework
>> powerpc: introduce arch_enter_from_user_mode
>> powerpc: Introduce syscall exit arch functions
>> powerpc: add exit_flags field in pt_regs
>> powerpc: Prepare for IRQ entry exit
>> powerpc: Enable IRQ generic entry/exit path.
>> powerpc: Enable Generic Entry/Exit for syscalls.
>>
>> arch/powerpc/Kconfig | 2 +
>> arch/powerpc/include/asm/entry-common.h | 539 ++++++++++++++++++++++++
>> arch/powerpc/include/asm/hw_irq.h | 4 +-
>> arch/powerpc/include/asm/interrupt.h | 401 +++---------------
>> arch/powerpc/include/asm/ptrace.h | 3 +
>> arch/powerpc/include/asm/stacktrace.h | 6 +
>> arch/powerpc/include/asm/syscall.h | 5 +
>> arch/powerpc/include/asm/thread_info.h | 1 +
>> arch/powerpc/include/uapi/asm/ptrace.h | 14 +-
>> arch/powerpc/kernel/asm-offsets.c | 1 +
>> arch/powerpc/kernel/interrupt.c | 258 +++---------
>> arch/powerpc/kernel/ptrace/ptrace.c | 142 +------
>> arch/powerpc/kernel/signal.c | 8 +
>> arch/powerpc/kernel/syscall.c | 119 +-----
>> arch/powerpc/kernel/traps.c | 2 +-
>> arch/powerpc/kernel/watchdog.c | 2 +-
>> arch/powerpc/perf/core-book3s.c | 2 +-
>> 17 files changed, 693 insertions(+), 816 deletions(-)
>> create mode 100644 arch/powerpc/include/asm/entry-common.h
>>
> Hi,
>
> I have reviewed and tested the generic IRQ entry/exist patch series.
> Below are my observations:
>
>
Test Coverage
> • Successfully ran LTP (specially syscall) and entire LTP test suite,
> without observing any regressions or issues related to the
> implementation.
>
>
System Configuration
> • CPUs: 160
> • Kernel: v6.18.0-rc1+
> • Processor mode: Shared (uncapped)
>
>
Performance Evaluation
> • Conducted benchmarking using perf bench syscall basic -l and
> hackbench.
> • No functional regressions observed, and results were consistent with
> expectations.
>
> • Results for perf bench syscall**Loops = 100,000**
> **Loops = 100,000**
> | Metric | W/O Generic Framework | With Generic Framework
> | Improvement |
> |----------|-----------------------:|-----------------------:|------------:|
>
> | usecs/op | 0.125328 | 0.128839
> | ~-2.80% |
> | ops/sec | 7,979,645 | 7,762,047
> | ~-2.73% |
>
> **Loops = 1,000,000**
> | Metric | W/O Generic Framework | With Generic
> Framework | Improvement |
> |----------|-----------------------:|-----------------------:|------------:|
>
> | usecs/op | 0.125015 | 0.127885
> | ~-2.30% |
> | ops/sec | 7,999,051 | 7,819,546
> | ~-2.24% |
>
> **Loops = 10,000,000**
> | Metric | W/O Generic Framework | With Generic Framework
> | Improvement |
> |----------|-----------------------:|-----------------------:|------------:|
>
> | usecs/op | 0.124613 | 0.127426
> | ~-2.26% |
> | ops/sec | 8,024,827 | 7,847,735
> | ~-2.21% |
>
> **Overall (aggregated across all runs)**
> | Metric | W/O Generic Framework | With Generic Framework
> | Improvement |
> | ---------- |
> ---------------------:|-----------------------:|------------:|
> | Total time | 1.384 [sec] | 1.415 [sec]
> | ~-2.27% |
> | usecs/op | 0.124656 | 0.127480
> | ~-2.27% |
> | ops/sec | 8,022,098 | 7,844,423
> | ~-2.21% |
>
> A 2% performance degradation was observed with the perf bench syscall.
>
> • Results for hackbench
>
> | Metric | W/O Generic Framework | With Generic Framework
> | Improvement |
> |----------|----------------------
> :|-----------------------:|------------:|
> | Min Time | 142.055 (sec). | 141.699 (sec)
> | 0.25%
> | Max Time | 143.791 (sec). | 143.206 (sec)
> | 0.41%
> | Avg Time | 142.925 (sec) | 142.472 (sec)
> | 0.32%
>
> So overall 0.3 % improvement is observed across 10 runs.
>
> Please add below tag for the patch set.
>
Tested-by: Samir M <samir at linux.ibm.com>
> Thank You !!
>
>
> Regards,
> Samir.
>
Hi,
Apologies for the earlier email. The benchmark results table was not
properly formatted in that version, so I am re-sending the results below
for clarity.
I have reviewed and tested the generic IRQ entry/exist patch series.
Below are my observations:
Test Coverage
• Successfully ran LTP (specially syscall) and entire LTP test suite,
without observing any regressions or issues related to the implementation.
System Configuration
• CPUs: 160
• Kernel: v6.18.0-rc1+
• Processor mode: Shared (uncapped)
Performance Evaluation
• Conducted benchmarking using perf bench syscall basic -l and hackbench.
• No functional regressions observed, and results were consistent with
expectations.
• Results for perf bench syscall
Loops = 100,000
+-----------+------------------------+------------------------+------------+
| Metric | W/O Generic Framework | With Generic Framework |
Improvement |
+-----------+------------------------+------------------------+------------+
| usecs/op | 0.125328 | 0.128839
| ~-2.80% |
| ops/sec | 7,979,645 | 7,762,047
| ~-2.73% |
+-----------+------------------------+------------------------+------------+
Loops = 1,000,000
+-----------+------------------------+------------------------+------------+
| Metric | W/O Generic Framework | With Generic Framework |
Improvement |
+-----------+------------------------+------------------------+------------+
| usecs/op | 0.125015 | 0.127885
| ~-2.30% |
| ops/sec | 7,999,051 | 7,819,546
| ~-2.24% |
+-----------+------------------------+------------------------+------------+
Loops = 10,000,000
+-----------+------------------------+------------------------+------------+
| Metric | W/O Generic Framework | With Generic Framework |
Improvement |
+-----------+------------------------+------------------------+------------+
| usecs/op | 0.124613 | 0.127426
| ~-2.26% |
| ops/sec | 8,024,827 | 7,847,735
| ~-2.21% |
+-----------+------------------------+------------------------+------------+
Overall (aggregated across all runs)
+-------------+------------------------+------------------------+----------+
| Metric | W/O Generic Framework | With Generic Framework |
Improvement |
+-------------+------------------------+------------------------+----------+
| Total time | 1.384 [sec] | 1.415 [sec]
| ~-2.27% |
| usecs/op | 0.124656 | 0.127480
| ~-2.27% |
| ops/sec | 8,022,098 | 7,844,423
| ~-2.21% |
+-------------+------------------------+------------------------+----------+
A 2% performance degradation was observed with the perf bench syscall.
• Results for hackbench
+-----------+---------------------------+---------------------------+------+
| Metric | W/O Generic Framework | With Generic Framework
| Improvement |
+-----------+---------------------------+---------------------------+------+
| Min Time | 142.055 (sec) | 141.699
(sec) | +0.25% |
| Max Time | 143.791 (sec) | 143.206 (sec)
| +0.41% |
| Avg Time | 142.925 (sec) | 142.472 (sec)
| +0.32% |
+-----------+---------------------------+---------------------------+------+
So overall 0.3 % improvement is observed across 10 runs.
Please add below tag for the patch set.
Tested-by: Samir M <samir at linux.ibm.com>
Thank You !!
Regards,
Samir.
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