linux-kernel - Re: [PATCH 0/3] x86: Use static_call for three smp

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Message-ID: <20260108115143.GK272712@noisy.programming.kicks-ass.net>
Date: Thu, 8 Jan 2026 12:51:43 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Eric Dumazet <edumazet@...gle.com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
	"H . Peter Anvin" <hpa@...or.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [PATCH 0/3] x86: Use static_call for three smp_ops methods

On Mon, Dec 22, 2025 at 08:14:03PM +0000, Eric Dumazet wrote:
> Busy hosts with RFS enabled can send more than 6,000,000 IPI
> per second. arch_send_call_function_single_ipi() is currently
> using an indirect call (because Xen can override the target).
> 
> Indirect calls are expensive on some platforms with retpoline.
> 
> This series converts three smp_ops methods to static_call
> infrastructure to remove common indirect calls.
> 
> Eric Dumazet (3):
>   x86/smp: Use static_call for arch_send_call_function_single_ipi()
>   x86/smp: Use static_call for arch_smp_send_reschedule()
>   x86/smp: Use static_call for arch_send_call_function_ipi()
> 
>  arch/x86/include/asm/smp.h | 23 +++++++++++++++++------
>  arch/x86/kernel/smp.c      | 19 +++++++++++++++++++
>  arch/x86/xen/smp_hvm.c     |  1 +
>  arch/x86/xen/smp_pv.c      |  1 +
>  4 files changed, 38 insertions(+), 6 deletions(-)

Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>