From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 8BA0F4398EB for ; Tue, 4 Aug 2026 22:01:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785880891; cv=none; b=X5encYKGszUwp7Lwgm8k4cwh1bf3FjVPYkouQ5wwHlvvtBK4X30V4pzjFfSHPqzLGq67rahOO0F+CJAys0trtr4jctdmhrW8+3LRTXJr2BeR+LFeFDi6BcN7Rg4NQX+hzUw1TtDrVVIK/8msKHyxhGWN0yR4hhE4CbQ2PihKmWs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785880891; c=relaxed/simple; bh=Dt15N3xs9qbmFZWyVp1vNCE2Z24OUAnKlUREODpU20A=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=NYYgmEFQo2QJx/3Vzg7iLLa9qQSepiIqwvIDqLlIdWv74QPFerQCr85z3OItqSB+WeKMmPzd2+VrOQOxSj3o8ZVe8ZyDIgZhSAB4YpQXDOYESiXEYdFRBW5n25TSy/bnmYKcXnGwcNwvhL+lDkEPmr0mzanGaJO8iFsP3vTJNuM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=kAjw7zJu; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="kAjw7zJu" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0D1001F000E9; Tue, 4 Aug 2026 22:01:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785880890; bh=wUuLD8pBXpxetyWSDP6sLwCx7hfJucK9OdsS4BwclOA=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=kAjw7zJu6exQmrGC2lB1KRNaAMyyXdP5zNcwwsxzJN3yYvdjwq2FQPEGrwoGc/uQ9 EEoYiJT6sfuDPBk9VFp23uX7QZSc5r/PJQdHmzNH+2rc0ZHooSkpNqCngF4SLCdJtY ORAGz3f0eo12Gy+YG5MyyeyOiGS31NAvx1g97a5fvhtAytRAtMzvLPEk3xLNlxKemq yEmvF6eNsopNkIsuo+EIREPNBC/n1Z7/lNVlkGCreiXSCLC8OtQoqS9oyyRpdlOS/8 4+GXN3PvOjEIpycgoZO8M2neVs2cc68J8FZBIEz6Tg8+VzHDpxOx/5JkHxnMQnrUGY JAQpxBe2spC+Q== Message-ID: <44a20360-c791-491d-bd84-e161b7c6a9f0@kernel.org> Date: Wed, 5 Aug 2026 00:01:22 +0200 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: [RFC v2 PATCH 0/16] Optimize this_cpu_*() ops for non-x86 (ARM64 for this series) To: "Christoph Lameter (Ampere)" Cc: "Lorenzo Stoakes (ARM)" , Linus Torvalds , Mark Rutland , Yang Shi , Ryan Roberts , dennis@kernel.org, tj@kernel.org, urezki@gmail.com, catalin.marinas@arm.com, will@kernel.org, akpm@linux-foundation.org, hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Jason Gunthorpe References: <0344c559-1959-4531-9265-d5a5180eb7cd@arm.com> <25d1e09b-53e4-7cd5-87db-b58437e4e690@gentwo.org> <4887267b-dc26-4c33-96ca-8dff054a0d1f@kernel.org> <8d6119c7-2216-fcdd-d0b9-cc60ccc8caf3@gentwo.org> <4baf6edb-c84b-4da9-b905-4d40d4bf5fdc@kernel.org> <7f2b2030-b912-70ee-5019-02dad2e87ca6@gentwo.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 8/4/26 23:56, Christoph Lameter (Ampere) wrote: > On Tue, 4 Aug 2026, David Hildenbrand (Arm) wrote: > >>> These are operations that are key to the performance in critical parts of >>> memory management and this code is replicated by being inlined thousands >>> of times in the kernel. >> >> Cool, then it is easy to show the difference by running micro + macro benchmarks. > > And we have done so repeatedly. Look at Yang's posts. > I'm getting tired of this. So to be clear: claiming that the additional instructions are unacceptable I'd expect something minimal like: "removing these 3 instructions speeds up micro-benchmark (a, b, c) by X% and macro-benchmarks (d, e, f) by Y% compared to Mark's approach". [1] https://lore.kernel.org/r/ea268481-d584-4744-99d6-0b05aade7d5d@kernel.org -- Cheers, David