From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 8782225B1CB; Wed, 18 Feb 2026 09:33:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771407199; cv=none; b=ZFTiRgnYO2Lou2tsjfJNp09JTIX36qSYQTKTKnMUxueh8dXcc71yMC023CkPY8RodWOHOl2FEQY8CaoAi/izI5Jj5Cr3PPoUe8PEKopReAnCABDbD3l+V0NkybYYOEH8zOEM0wqTzLZ/605EM86u/TJbj1zo6gGFQ12XSOjSako= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771407199; c=relaxed/simple; bh=wcEMXbKiNhnJK2jtdP1o2fxrBt6Qe2aee6ayozsX44k=; h=Message-ID:Date:MIME-Version:Subject:From:To:Cc:References: In-Reply-To:Content-Type; b=ANiAj+bzJN3Cj3P8FuPIhO3DvJgaapO57F8RxRXWJZzHILO8P5gM8TQdpJvsbzpRIdJn8Pe+9yuka/WsMgl7IhbOF9dn9H/7bCkeGeFtnPFKyaiJXkNU8pTW+MreSyR/A/2rtACbYxfS3HWOpUl7Qg52B2ITo+nSZdkE/HjgTxs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id AF2021477; Wed, 18 Feb 2026 01:33:11 -0800 (PST) Received: from [10.57.81.199] (unknown [10.57.81.199]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 281A43F7F5; Wed, 18 Feb 2026 01:33:15 -0800 (PST) Message-ID: Date: Wed, 18 Feb 2026 09:33:14 +0000 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 6.6 0/3] arm64: Speed up boot with faster linear map creation Content-Language: en-GB From: Ryan Roberts To: Greg KH Cc: stable@vger.kernel.org, catalin.marinas@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Jack Aboutboul , Sharath George John , Noah Meyerhans , Jim Perrin References: <20260217133411.2881311-1-ryan.roberts@arm.com> <2026021700-chafe-jurist-cb24@gregkh> <17c9efaf-6c33-4485-bde2-345cc15ac000@arm.com> <2026021718-citrus-parakeet-dc60@gregkh> <7f30a8e4-49c3-421d-be05-08afb544aa41@arm.com> <2026021758-subsidy-tinfoil-ee2c@gregkh> <20e320d2-749a-4379-a236-5dbe3d52b07f@arm.com> In-Reply-To: <20e320d2-749a-4379-a236-5dbe3d52b07f@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 17/02/2026 14:43, Ryan Roberts wrote: > On 17/02/2026 14:26, Greg KH wrote: >> On Tue, Feb 17, 2026 at 02:21:30PM +0000, Ryan Roberts wrote: >>> On 17/02/2026 14:10, Greg KH wrote: >>>> On Tue, Feb 17, 2026 at 01:58:36PM +0000, Ryan Roberts wrote: >>>>> On 17/02/2026 13:50, Greg KH wrote: >>>>>> On Tue, Feb 17, 2026 at 01:34:05PM +0000, Ryan Roberts wrote: >>>>>>> Hi All, >>>>>>> >>>>>>> This series is a backport that applies to stable kernel 6.6 (base v6.6.126), for >>>>>>> some speed ups to enable significantly faster booting on systems with a lot of >>>>>>> memory. The patches were originally posted at: >>>>>>> >>>>>>> https://lore.kernel.org/linux-arm-kernel/20240412131908.433043-1-ryan.roberts@arm.com/ >>>>>>> >>>>>>> ... and were originally merged upstream in v6.10-rc1. >>>>>>> >>>>>>> I'm requesting this be merged to stable on behalf of a partner who wants to get >>>>>>> the benefit of this series in Debian 12. >>>>>> >>>>>> Why can't they just use a newer kernel version (i.e. 6.12)? Surely they >>>>>> would be able to justify moving to a newer kernel for performance >>>>>> reasons, why enable them to stay on an older one, just delaying the >>>>>> inevitable upgrade they will have to do anyway in a year or so? >>>>> >>>>> I can't answer this presicely, but I did ask and push for that approach. As I >>>>> understand it, they are stuck with Debian 12, which is stuck with kernel 6.1. >>>>> The Debian maintainer apparently requested that these go through stable in order >>>>> to get them into Debian 12. >>>> >>>> I understand the position of Debian not wanting to take patches for new >>>> features that are not already upstream, but really, Debian offers a >>>> newer kernel for hardware that wants to use it for things like this, >>>> right? Why not just use that instead? >>> >>> Let me go push a bit harder. But I expect we are in the grey zone between bug >>> and feature here; this is a performance bug fix, not a new feature. By >>> selectively backporting I'm guessing they are avoiding the risk of new features >>> that a new kernel brings introducing new bugs? I'm guessing there is a higher >>> qualification bar for that. >> >> That's a broken "qualification system" if that is the case, given that >> the patches that flow back into stable kernel releases should be >> triggering "full qualification" if anyone actually paid attention to >> what goes into there :) >> >> Anyway, good luck! And same for 6.1.y, if they are ok with 6.6.y, why >> would they even care about 6.1.y? > > The request was only for 6.1. I did 6.6 as well for continuity; I didn't want it > to get slow again if they moved from 6.1 to 6.6. It's already fixed in 6.12. Hi Greg, I thought a bit more about this overnight, and decided I wanted to have one more go at convincing you... In case you didn't read the commit logs, this series fixes a pretty nasty performace bug; for a machine with 512G of RAM, it previously took 17.5 seconds to create the linear map, and with the changes, it's down to 1.2 seconds. That's quite a big quality-of-life improvement if you are booting VMs regularly. (personally I hit this quite a bit). It's a low risk change - it's been in since v6.10 and is part of arm64's core boot path - and no issues have ever been raised. Are you sure this isn't the sort of change that should be considered for stable? Thanks, Ryan > > >> >> thanks, >> >> greg k-h >