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 6A39C4F6465 for ; Mon, 7 Sep 2026 13:59:05 +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=1788789547; cv=none; b=OiECCuzXf46OsAo0od2ylqCjsoVQUecSBr0k07qt4st0pbneaO/F2CfnFP+eBUMbCZzWWEsONG+tYnVqUx5I+NajNUd3yuYtmzGndfxBhELPHeVsmyCXGNG8S4RN0KoYM9tlI/1JrDSPqQpK29pnE7FRpEW7PqCUHmQMU9flbzU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788789547; c=relaxed/simple; bh=KANePYIkrVNp1cnhNyd6G+q8PZ8ZhUnLtrRM+g7sCN0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=LMNuvML9OWqO1tmDbvBzz1T0vBWcAfEqVHB0QnagJtT/K4wurlerRlc01S1P5aQPzHjW2lxx6Lky5d8DDhmaen8sDi73FVkHVoLYAX4+9bISolTPdpxIX8brirjWEdQDX36L/Tl6eQC1SFK7IuL7URXUEtXubhqWmmub2U39y+U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ixHulrZx; 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="ixHulrZx" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EC4621F00A3E; Mon, 7 Sep 2026 13:59:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788789545; bh=V+1QIqU52AVFPMroKZLyqFAwYP3b20aWfmSMgRX5j9U=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=ixHulrZxrmJT9lfSwaDj4SWjTvLSrkbTPBYKU+Fg1+sffniB11uyw1qCzpuRdYiPk zUgv+2NJ40uemHK8XhXsJOpt4wt7YiN9kzADUr+JnCKuYxU9CiAYDCFpqxge7IYxBA JOxsmcRLr6fYAGMULodWLhhHGKphKgZXC0r3XPjg8BORNg3KNbXumftopqVU6lmYjj +I2KxYz8OU52dWkzagqLJVmx3afd77dfhk/xPqvnfRcwUGz4m+/PRGDT0e9nPlW0NG gY9nNDSFFWRR45lAQwhZXJphqNBH3T35d4hIu/LtSMOLiYLF0P1AdSGi3buftlb1PB NJjV3anxHrL/Q== Message-ID: Date: Mon, 7 Sep 2026 15:59:02 +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: [PATCH] mm: vmpressure: scale window size based on machine memory To: Taha Sezer , ljs@kernel.org, akpm@linux-foundation.org Cc: vbabka@kernel.org, mhocko@suse.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260831130316.448-1-tahasezer.is@gmail.com> <6a9673f4.cbade83c.66f7c.3d66@mx.google.com> 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 9/1/26 08:43, Taha Sezer wrote: > Hi Lorenzo, Andrew, > > Thanks for the honest and thorough review. > > Lorenzo -- yes, I did use an AI coding assistant (Claude) to help > write this patch. I should have included an Assisted-by: tag from > the start and I apologise for the omission. That was a mistake on > my part, not an attempt to hide anything -- I simply was not aware of > the disclosure process for my first submission. > > Andrew -- you are absolutely right about the math. The original window > is SWAP_CLUSTER_MAX * 16 = 512 pages, and my formula clamp(fls(mem), > 4, 64) produces values well below 16 for every machine under ~8 TB. > The patch shrinks the window on virtually all real hardware, which is > the exact opposite of what the commit message promises. Embarrassing, > and I should have caught this before sending. > > For a bit of context on why I chose mm/: I have been writing a hobby > kernel from scratch (Caelum) that includes a VMM with COW and demand > paging, a slab allocator with NUMA-aware allocation, TLB shootdown > via IPI, and SMP boot -- so memory management is the area I am most > comfortable with. That said, comfortable with the concepts clearly > did not save me from a basic arithmetic mistake here, and I take full > responsibility for not verifying the output carefully enough. > > Before I send a v2, I would appreciate any guidance: > > 1. Is the general idea still worth pursuing -- scaling the window > logarithmically with total RAM using fls(), or do you think > the fixed 512-page window is fine as-is and this TODO is > better left alone? > > 2. If the approach is worth fixing: would keeping the original > multiplier of 16 as the floor (so the window only ever grows > beyond 512 pages) be the right direction, or would you prefer > a different scaling strategy entirely? > > 3. Any other advice for a first-time contributor on how to > approach mm/ patches more carefully? > > I will hold off on v2 until I hear back, so I do not waste anyone's > time with another half-baked attempt. The next version will include > a proper Assisted-by: Claude:claude-opus-4 tag. Note that we now prefer Assisted-by: LLM -- Cheers, David