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Message-ID: <fe290d99-e81b-4af1-ac2f-5b2a603f2311@linux.ibm.com>
Date: Fri, 23 Jan 2026 23:24:15 +0530
From: Shrikanth Hegde <sshegde@...ux.ibm.com>
To: Mukesh Kumar Chaurasiya <mkchauras@...ux.ibm.com>, maddy@...ux.ibm.com,
chleroy@...nel.org, linuxppc-dev@...ts.ozlabs.org
Cc: npiggin@...il.com, ryabinin.a.a@...il.com, glider@...gle.com,
andreyknvl@...il.com, dvyukov@...gle.com, vincenzo.frascino@....com,
oleg@...hat.com, kees@...nel.org, luto@...capital.net,
wad@...omium.org, mchauras@...ux.ibm.com, thuth@...hat.com,
ruanjinjie@...wei.com, akpm@...ux-foundation.org, charlie@...osinc.com,
deller@....de, ldv@...ace.io, macro@...am.me.uk,
segher@...nel.crashing.org, peterz@...radead.org,
bigeasy@...utronix.de, namcao@...utronix.de, tglx@...utronix.de,
mark.barnett@....com, linux-kernel@...r.kernel.org,
kasan-dev@...glegroups.com, mpe@...erman.id.au
Subject: Re: [PATCH v4 0/8] Generic IRQ entry/exit support for powerpc
Hi Mukesh.
On 1/23/26 1:09 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 are below:
>
> perf bench syscall usec/op (-ve is improvement)
>
> | Syscall | Base | test | change % |
> | ------- | ----------- | ----------- | -------- |
> | basic | 0.093543 | 0.093023 | -0.56 |
> | execve | 446.557781 | 450.107172 | +0.79 |
> | fork | 1142.204391 | 1156.377214 | +1.24 |
> | getpgid | 0.097666 | 0.092677 | -5.11 |
>
> perf bench syscall ops/sec (+ve is improvement)
>
> | Syscall | Base | New | change % |
> | ------- | -------- | -------- | -------- |
> | basic | 10690548 | 10750140 | +0.56 |
> | execve | 2239 | 2221 | -0.80 |
> | fork | 875 | 864 | -1.26 |
> | getpgid | 10239026 | 10790324 | +5.38 |
>
>
> IPI latency benchmark (-ve is improvement)
>
> | Metric | Base (ns) | New (ns) | % Change |
> | -------------- | ------------- | ------------- | -------- |
> | Dry run | 583136.56 | 584136.35 | 0.17% |
> | Self IPI | 4167393.42 | 4149093.90 | -0.44% |
> | Normal IPI | 61769347.82 | 61753728.39 | -0.03% |
> | Broadcast IPI | 2235584825.02 | 2227521401.45 | -0.36% |
> | Broadcast lock | 2164964433.31 | 2125658641.76 | -1.82% |
>
>
> 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:
> V3 -> V4
> - Fixed the issue in older gcc version where linker couldn't find
> mem functions
> - Merged IRQ enable and syscall enable into a single patch
> - Cleanup for unused functions done in separate patch.
> - Some other cosmetic changes
> V3: https://lore.kernel.org/all/20251229045416.3193779-1-mkchauras@linux.ibm.com/
>
> V2 -> V3
> - #ifdef CONFIG_GENERIC_IRQ_ENTRY removed from unnecessary places
> - Some functions made __always_inline
> - pt_regs padding changed to match 16byte interrupt stack alignment
> - And some cosmetic changes from reviews from earlier patch
> V2: https://lore.kernel.org/all/20251214130245.43664-1-mkchauras@linux.ibm.com/
>
> V1 -> V2
> - Fix an issue where context tracking was showing warnings for
> incorrect context
> V1: https://lore.kernel.org/all/20251102115358.1744304-1-mkchauras@linux.ibm.com/
>
> RFC -> PATCH V1
> - 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 GENERIC_ENTRY feature
> powerpc: Remove unused functions
>
> arch/powerpc/Kconfig | 1 +
> arch/powerpc/include/asm/entry-common.h | 533 ++++++++++++++++++++++++
> arch/powerpc/include/asm/hw_irq.h | 4 +-
> arch/powerpc/include/asm/interrupt.h | 386 +++--------------
> arch/powerpc/include/asm/kasan.h | 15 +-
> arch/powerpc/include/asm/ptrace.h | 6 +-
> arch/powerpc/include/asm/signal.h | 1 -
> 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/interrupt.c | 254 ++---------
> arch/powerpc/kernel/ptrace/ptrace.c | 142 +------
> arch/powerpc/kernel/signal.c | 25 +-
> 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 +-
> 18 files changed, 690 insertions(+), 828 deletions(-)
> create mode 100644 arch/powerpc/include/asm/entry-common.h
>
Ran it a bit on powernv (power9) too. Not warnings and similar
micro benchmark numbers.
I think this is in better shape now. With that,
for the series.
Reviewed-by: Shrikanth Hegde <sshegde@...ux.ibm.com>
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