From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 2C229EA4FBA for ; Mon, 23 Feb 2026 13:00:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=XWpeoNy1D03nd+2y1T3gOuhEjAr9cvPUV+WQbj5qUgU=; b=f/e2lUTzY9VgyEC6s7nNKkK/RE dX7CFWgKJ4zWrqt00G+nsXwqkwZlGXoO8+ghFoU/XJ3CH9e/8HLM+k96n8t1+/RoOW/70G12oSy3i ak4MJIjPpk4Xj96thvk8aa8y28TQQw/DWoOkCIHshom0ftBQ8Y5o4A1t8eEHdwdHMhldCHDlHsJMw YBI1Uzfd0sbpIUadvCNI3Ci5wqRcASsMR6XMC7qS5Pl6DgVgpe1WRTrSpPrPdZekF5B2c8xpPSfU1 QjYLNHD2t6Rd12+w2q/p2CDJGInGqdFjdTGx/ekzLXUkdcC5dciP6j8rAXWlXyNgTJ1FeDbrlLhns YLC4pcXA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vuVY8-00000000Jlk-0wwb; Mon, 23 Feb 2026 13:00:32 +0000 Received: from tor.source.kernel.org ([172.105.4.254]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vuVY7-00000000Jla-1y4y; Mon, 23 Feb 2026 13:00:31 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 6FF9A600C4; Mon, 23 Feb 2026 13:00:30 +0000 (UTC) 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> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <877bs4wi0c.ffs@tglx> X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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