linux-kernel - Re: [RFC V1 0/6] Generic Entry/Exit support for ppc64

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Message-ID: <tuylzfyyxfexl4fqid4xqo3bkxc25kkr3kah72ndexfw7qradv@xdqz7qxaliyf>
Date: Mon, 28 Apr 2025 21:22:15 +0530
From: Mukesh Kumar Chaurasiya <mchauras@...ux.ibm.com>
To: linux-kernel@...r.kernel.org
Cc: maddy@...ux.ibm.com, mpe@...erman.id.au, npiggin@...il.com,
        christophe.leroy@...roup.eu, naveen@...nel.org,
        neeraj.upadhyay@...nel.org, vschneid@...hat.com, tglx@...utronix.de,
        frederic@...nel.org, ankur.a.arora@...cle.com, sshegde@...ux.ibm.com,
        bigeasy@...utronix.de, kees@...nel.org, oleg@...hat.com,
        peterz@...radead.org, tzimmermann@...e.de, namcao@...utronix.de,
        kan.liang@...ux.intel.com, mcgrof@...nel.org, rppt@...nel.org,
        atrajeev@...ux.vnet.ibm.com, anjalik@...ux.ibm.com,
        coltonlewis@...gle.com, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [RFC V1 0/6] Generic Entry/Exit support for ppc64

On Mon, Apr 28, 2025 at 08:52:20PM +0530, Mukesh Kumar Chaurasiya wrote:

Few corrections in the commit message:
> This is a syscall only implementation of generic entry/exit framework
> for framework for ppc. IRQ handling is not done in this RFC. 
>
s/framework for framework/framework
> This will break the ppc32 build as of now which will be fixed along with
> IRQ handling.
> 
> Below are the performance benchmarks from perf bench basic syscall.
> This is for 1,00,00,000 getppid() calls
> 
> | Metric     | Without Generic Framework | With Generic Framework |
> | ---------- | ------------------------- | ---------------------- |
> | Total time | 0.904 [sec]               | 0.856 [sec]            |
> | usecs/op   | 0.090403                  | 0.085638               |
> | ops/sec    | 1,10,61,579               | 1,16,77,086            |
>
The coloums are reversed here

| Metric     | With Generic Framework    | Without Generic Framework |
| ---------- | ------------------------- | ------------------------- |
| Total time | 0.904 [sec]               | 0.856 [sec]               |
| usecs/op   | 0.090403                  | 0.085638                  |
| ops/sec    | 1,10,61,579               | 1,16,77,086               |

> That's ~5% degradation as of now.
> 
> Mukesh Kumar Chaurasiya (6):
>   powerpc: rename arch_irq_disabled_regs
>   powerpc: Prepare to build with genreic entry/exit framework
>   powerpc: introduce arch_enter_from_user_mode
>   powerpc: Add flag in paca for register restore state
>   powerpc: Introduce syscall exit arch functions
>   powerpc: Enable Generic Entry/Exit for syscalls.
> 
>  arch/powerpc/Kconfig                    |   1 +
>  arch/powerpc/include/asm/entry-common.h | 158 ++++++++++++++++++++++++
>  arch/powerpc/include/asm/hw_irq.h       |   4 +-
>  arch/powerpc/include/asm/interrupt.h    | 117 +++++++++++++++++-
>  arch/powerpc/include/asm/paca.h         |   1 +
>  arch/powerpc/include/asm/stacktrace.h   |   8 ++
>  arch/powerpc/include/asm/syscall.h      |   5 +
>  arch/powerpc/include/asm/thread_info.h  |   1 +
>  arch/powerpc/kernel/interrupt.c         | 153 ++++++-----------------
>  arch/powerpc/kernel/ptrace/ptrace.c     | 103 ---------------
>  arch/powerpc/kernel/signal.c            |   8 ++
>  arch/powerpc/kernel/syscall.c           | 117 +-----------------
>  arch/powerpc/kernel/traps.c             |   2 +-
>  arch/powerpc/kernel/watchdog.c          |   2 +-
>  arch/powerpc/perf/core-book3s.c         |   2 +-
>  15 files changed, 336 insertions(+), 346 deletions(-)
>  create mode 100644 arch/powerpc/include/asm/entry-common.h
> 
> -- 
> 2.49.0
>