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 A7E6C2D8781 for ; Thu, 6 Nov 2025 06:44:41 +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=1762411481; cv=none; b=lg/qm55w0AlkUM+ypnS5LFesb+Pggjq94lIFnPvz35GLAx66dEmURO6a6RhD+Gsg418Ul2h+4Y1wjdQetw7rsmeLOiBXHLTY2v4Hlv17CdJRWg/xhLdQuCVY1Q+x82uKjnydTv0WlfwZAMuF/Jc9SsdzPQSq/5uwohrH2BZFsA8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762411481; c=relaxed/simple; bh=ZiKKOJ05KAu/YBIRZGdhy0ZwdJrprSmfpvaH3VMvPz0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=LkZxI8pK483kEtC6gbYCULFCaVAicrS6RvuNgPIY5W9m+/IFL/5CUUZXcY/HeBVwMJIgqJIiPjy9wizkkeA3N3fghH9M2KBLKYnzNEAZejZT9skLDWOZ/1GJEBd7ZXxEvwXBlrEKF9pgfHqCKlTKqUVJzGKHixboDcC6OfsRQ1k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=qnQbW4nc; 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="qnQbW4nc" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 79C43C4CEF7; Thu, 6 Nov 2025 06:44:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1762411481; bh=ZiKKOJ05KAu/YBIRZGdhy0ZwdJrprSmfpvaH3VMvPz0=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=qnQbW4nc56UGrXYhNa5+GH9pyRlUxqdl3KwlMIur+x9pATNYccXvMn4KecebUevlH 2O9h0FP+c/9Ayv691bzxXcm6CpElUnp+fL1la7/+gPCZvLFfxeIE0bEAqiar+Gm7YL 7iS5LBfPs2bHC3laeLUXoLV2ZbXxFaigyQS7KqLOSwLxgFfURTI8nvdlZ5wvyPMZTv P+oWQvNTWTLSSrR7i/e/tCPl8hAu4lCwQF6FHhaWW5CyAXr17Oc/95SDNdwlPwNikm D8QlHdy86Ll474lnIJV5gwF+wEh9ZbkBGgWO58ELmxTwyMcjLslkZEVfPZi/VPmNvO Oqt1dnd0Gv+Yg== Message-ID: Date: Thu, 6 Nov 2025 07:44:37 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] x86/irq: Precompute nr_legacy_irqs() for performance optimization To: ray , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen Cc: x86@kernel.org, "H . Peter Anvin" , linux-kernel@vger.kernel.org References: Content-Language: en-US From: Jiri Slaby Autocrypt: addr=jirislaby@kernel.org; keydata= xsFNBE6S54YBEACzzjLwDUbU5elY4GTg/NdotjA0jyyJtYI86wdKraekbNE0bC4zV+ryvH4j rrcDwGs6tFVrAHvdHeIdI07s1iIx5R/ndcHwt4fvI8CL5PzPmn5J+h0WERR5rFprRh6axhOk rSD5CwQl19fm4AJCS6A9GJtOoiLpWn2/IbogPc71jQVrupZYYx51rAaHZ0D2KYK/uhfc6neJ i0WqPlbtIlIrpvWxckucNu6ZwXjFY0f3qIRg3Vqh5QxPkojGsq9tXVFVLEkSVz6FoqCHrUTx wr+aw6qqQVgvT/McQtsI0S66uIkQjzPUrgAEtWUv76rM4ekqL9stHyvTGw0Fjsualwb0Gwdx ReTZzMgheAyoy/umIOKrSEpWouVoBt5FFSZUyjuDdlPPYyPav+hpI6ggmCTld3u2hyiHji2H cDpcLM2LMhlHBipu80s9anNeZhCANDhbC5E+NZmuwgzHBcan8WC7xsPXPaiZSIm7TKaVoOcL 9tE5aN3jQmIlrT7ZUX52Ff/hSdx/JKDP3YMNtt4B0cH6ejIjtqTd+Ge8sSttsnNM0CQUkXps w98jwz+Lxw/bKMr3NSnnFpUZaxwji3BC9vYyxKMAwNelBCHEgS/OAa3EJoTfuYOK6wT6nadm YqYjwYbZE5V/SwzMbpWu7Jwlvuwyfo5mh7w5iMfnZE+vHFwp/wARAQABzSFKaXJpIFNsYWJ5 IDxqaXJpc2xhYnlAa2VybmVsLm9yZz7CwXcEEwEIACEFAlW3RUwCGwMFCwkIBwIGFQgJCgsC BBYCAwECHgECF4AACgkQvSWxBAa0cEnVTg//TQpdIAr8Tn0VAeUjdVIH9XCFw+cPSU+zMSCH eCZoA/N6gitEcnvHoFVVM7b3hK2HgoFUNbmYC0RdcSc80pOF5gCnACSP9XWHGWzeKCARRcQR 4s5YD8I4VV5hqXcKo2DFAtIOVbHDW+0okOzcecdasCakUTr7s2fXz97uuoc2gIBB7bmHUGAH XQXHvdnCLjDjR+eJN+zrtbqZKYSfj89s/ZHn5Slug6w8qOPT1sVNGG+eWPlc5s7XYhT9z66E l5C0rG35JE4PhC+tl7BaE5IwjJlBMHf/cMJxNHAYoQ1hWQCKOfMDQ6bsEr++kGUCbHkrEFwD UVA72iLnnnlZCMevwE4hc0zVhseWhPc/KMYObU1sDGqaCesRLkE3tiE7X2cikmj/qH0CoMWe gjnwnQ2qVJcaPSzJ4QITvchEQ+tbuVAyvn9H+9MkdT7b7b2OaqYsUP8rn/2k1Td5zknUz7iF oJ0Z9wPTl6tDfF8phaMIPISYrhceVOIoL+rWfaikhBulZTIT5ihieY9nQOw6vhOfWkYvv0Dl o4GRnb2ybPQpfEs7WtetOsUgiUbfljTgILFw3CsPW8JESOGQc0Pv8ieznIighqPPFz9g+zSu Ss/rpcsqag5n9rQp/H3WW5zKUpeYcKGaPDp/vSUovMcjp8USIhzBBrmI7UWAtuedG9prjqfO wU0ETpLnhgEQAM+cDWLL+Wvc9cLhA2OXZ/gMmu7NbYKjfth1UyOuBd5emIO+d4RfFM02XFTI t4MxwhAryhsKQQcA4iQNldkbyeviYrPKWjLTjRXT5cD2lpWzr+Jx7mX7InV5JOz1Qq+P+nJW YIBjUKhI03ux89p58CYil24Zpyn2F5cX7U+inY8lJIBwLPBnc9Z0An/DVnUOD+0wIcYVnZAK DiIXODkGqTg3fhZwbbi+KAhtHPFM2fGw2VTUf62IHzV+eBSnamzPOBc1XsJYKRo3FHNeLuS8 f4wUe7bWb9O66PPFK/RkeqNX6akkFBf9VfrZ1rTEKAyJ2uqf1EI1olYnENk4+00IBa+BavGQ 8UW9dGW3nbPrfuOV5UUvbnsSQwj67pSdrBQqilr5N/5H9z7VCDQ0dhuJNtvDSlTf2iUFBqgk 3smln31PUYiVPrMP0V4ja0i9qtO/TB01rTfTyXTRtqz53qO5dGsYiliJO5aUmh8swVpotgK4 /57h3zGsaXO9PGgnnAdqeKVITaFTLY1ISg+Ptb4KoliiOjrBMmQUSJVtkUXMrCMCeuPDGHo7 39Xc75lcHlGuM3yEB//htKjyprbLeLf1y4xPyTeeF5zg/0ztRZNKZicgEmxyUNBHHnBKHQxz 1j+mzH0HjZZtXjGu2KLJ18G07q0fpz2ZPk2D53Ww39VNI/J9ABEBAAHCwV8EGAECAAkFAk6S 54YCGwwACgkQvSWxBAa0cEk3tRAAgO+DFpbyIa4RlnfpcW17AfnpZi9VR5+zr496n2jH/1ld wRO/S+QNSA8qdABqMb9WI4BNaoANgcg0AS429Mq0taaWKkAjkkGAT7mD1Q5PiLr06Y/+Kzdr 90eUVneqM2TUQQbK+Kh7JwmGVrRGNqQrDk+gRNvKnGwFNeTkTKtJ0P8jYd7P1gZb9Fwj9YLx jhn/sVIhNmEBLBoI7PL+9fbILqJPHgAwW35rpnq4f/EYTykbk1sa13Tav6btJ+4QOgbcezWI wZ5w/JVfEJW9JXp3BFAVzRQ5nVrrLDAJZ8Y5ioWcm99JtSIIxXxt9FJaGc1Bgsi5K/+dyTKL wLMJgiBzbVx8G+fCJJ9YtlNOPWhbKPlrQ8+AY52Aagi9WNhe6XfJdh5g6ptiOILm330mkR4g W6nEgZVyIyTq3ekOuruftWL99qpP5zi+eNrMmLRQx9iecDNgFr342R9bTDlb1TLuRb+/tJ98 f/bIWIr0cqQmqQ33FgRhrG1+Xml6UXyJ2jExmlO8JljuOGeXYh6ZkIEyzqzffzBLXZCujlYQ DFXpyMNVJ2ZwPmX2mWEoYuaBU0JN7wM+/zWgOf2zRwhEuD3A2cO2PxoiIfyUEfB9SSmffaK/ S4xXoB6wvGENZ85Hg37C7WDNdaAt6Xh2uQIly5grkgvWppkNy4ZHxE+jeNsU7tg= In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Hi, On 01. 11. 25, 12:26, ray wrote: > Precompute the return value of nr_legacy_irqs() in init_ISA_irqs(), > init_IRQ(), and native_init_IRQ() functions to avoid repeated function > calls in loops, improving performance. > > Changes made: > - Precompute nr_legacy_irqs() return value in three functions > - Use local variables instead of function calls in loops > - Maintain original logic unchanged > > Signed-off-by: ray Is this how you sign legal documents? > index 6ab9eac64670..bb7cbf99f65c 100644 > --- a/arch/x86/kernel/irqinit.c > +++ b/arch/x86/kernel/irqinit.c ... > @@ -66,7 +66,9 @@ void __init init_ISA_irqs(void) > > legacy_pic->init(0); > > - for (i = 0; i < nr_legacy_irqs(); i++) { > + nr_legacy = nr_legacy_irqs(); > + > + for (i = 0; i < nr_legacy; i++) { nr_legacy_irqs() is a static inline, so this was not a call per se. Instead, this resolves to 2 memory reads. Is the change worth it at all, provided these are NOT a fast path? > @@ -106,7 +112,9 @@ void __init native_init_IRQ(void) > > lapic_assign_system_vectors(); > > - if (!acpi_ioapic && !of_ioapic && nr_legacy_irqs()) { > + nr_legacy = nr_legacy_irqs(); > + > + if (!acpi_ioapic && !of_ioapic && nr_legacy) { What's the added value in here at all? thanks, -- js suse labs