From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8E8AE1EBA14; Mon, 23 Feb 2026 13:00:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771851630; cv=none; b=i2PnWFrrxwyRskUdu9oJEsiDMfEgVIDbY9OT/zZClgIJj+V/EitK/L0LMh2sCJzbGXD3iZvI/Gnhs1w3/S6NbP9pVvEIVBfcDCptdXBcAEyLEMPAZ0ETewiyD4X4HWFxTtKqkrq/bMgtZ4TbXmBEyZnK81GffN8p6Kb693tr08E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771851630; c=relaxed/simple; bh=uOtJDy2FyPxpMhP2bRO2gFMv/2nj4Vw849MMg7jCtgQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=UoHdyIxQfeW2JSph6qMBNSRhlriUEA6aXgBRtNoathMjPECR1jJ+w1cSy0d2tGdPLTkOCBjvZnFF7OEQYXKl/uQF4U9I87rcGM5T3Od8qHwJE1+d0XKr10V5+QFSnl628RHoCLmIFByJa+xHgvO1zIwBU19nkGQDzOFQqVfya+c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=clGrAsM1; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="clGrAsM1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 18D62C116C6; Mon, 23 Feb 2026 13:00:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1771851630; bh=uOtJDy2FyPxpMhP2bRO2gFMv/2nj4Vw849MMg7jCtgQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=clGrAsM1eO4t5380MKOhdLbYwfD37kNqsjhSPZfNmBaOz+46Aab5ZPI93qEZEU5nS DcwHN+ArfBxcohFQnPXImXwzoJa/FHhgA0Z9jrj3wh7XDmC3M+vqCxsmgfy4RSA5tt kkQBqXWtWNzYKtp35Gc+GZEl+P9QXOmoXkBRlX43RAI4LY7FuHvlHjYGeyDpC+RGBT tUqkFw7eNYiDbxZ/wRx1d7LsNHhur4YAEp9jJv9TLYXDgW2OX+BkEv5rWEz9yWRU0b nbhXvY0Av3j2c9EfjiEXgY8ljwW0Re4YGY8ls3P4Q9In+IRfQjjZq3NlZG1S3pcp07 1d/WixW1O9Mnw== Date: Mon, 23 Feb 2026 20:41:55 +0800 From: Jisheng Zhang To: Thomas Gleixner , ardb@kernel.org, mark.rutland@arm.com Cc: Catalin Marinas , Will Deacon , Arnd Bergmann , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Guo Ren , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-riscv@lists.infradead.org, linux-csky@vger.kernel.org Subject: Re: [PATCH 2/3] genirq: use runtime constant to optimize handle_arch_irq access Message-ID: References: <20260220090922.1506-1-jszhang@kernel.org> <20260220090922.1506-3-jszhang@kernel.org> <877bs4wi0c.ffs@tglx> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <877bs4wi0c.ffs@tglx> On Sun, Feb 22, 2026 at 11:06:11PM +0100, Thomas Gleixner wrote: > On Fri, Feb 20 2026 at 17:09, Jisheng Zhang wrote: > > Currently, on GENERIC_IRQ_MULTI_HANDLER platforms, the handle_arch_irq > > is a pointer which is set during booting, and every irq processing needs > > to access it, so it sits in hot code path. We can use the > > runtime constant mechanism which was introduced by Linus to speed up > > its accessing. > > The proper solution is to use a static call and update it in > set_handle_irq(). That removes the complete indirect call issue from > the hot path. + Ard, Mark, Good idea. The remaining problem is no static call support for current GENERIC_IRQ_MULTI_HANDLER (or similar, arm64 e.g) platforms. For arm64, Ard tried to add the static call support[1] in 2021, but Mark concerned "compiler could easily violate our expectations in future"[2], and asked for static calls "critical rather than a nice-to-have" usage. Hi Ard, Mark, Could this irq performance improvement be used as a "critical" usage for arm64 static call? Per my test, about 6.5% improvement was seen on quad CA55. Another alternative: disable static call if CFI is enabled, and give the platform/SoC users chance to enable static call to benefit from it. Any comment is appreciated. Thanks [1] https://www.spinics.net/lists/arm-kernel/msg931861.html [2] https://www.spinics.net/lists/arm-kernel/msg932481.html > > Thanks, > > tglx