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Date: Thu, 9 Jan 2025 12:10:17 +0000
From: Catalin Marinas <catalin.marinas@arm.com>
To: Zhenhua Huang <quic_zhenhuah@quicinc.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>, will@kernel.org,
	ardb@kernel.org, ryan.roberts@arm.com, mark.rutland@arm.com,
	joey.gouly@arm.com, dave.hansen@linux.intel.com,
	akpm@linux-foundation.org, chenfeiyang@loongson.cn,
	chenhuacai@kernel.org, linux-mm@kvack.org,
	linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
	quic_tingweiz@quicinc.com, stable@vger.kernel.org
Subject: Re: [PATCH v4] arm64: mm: Populate vmemmap/linear at the page level
 for hotplugged sections
Message-ID: <Z3-8qdluDbrDntRJ@arm.com>
References: <20250107074252.1062127-1-quic_zhenhuah@quicinc.com>
 <Z31--x4unDHRU5Zo@arm.com>
 <fbb134e0-cfeb-4c6e-98b4-d945f95383db@arm.com>
 <169f8006-ff33-48ca-a680-37fe1cf0efe8@quicinc.com>
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In-Reply-To: <169f8006-ff33-48ca-a680-37fe1cf0efe8@quicinc.com>

On Thu, Jan 09, 2025 at 03:04:48PM +0800, Zhenhua Huang wrote:
> On 2025/1/8 18:11, Anshuman Khandual wrote:
> > Just wondering why not start with PUD level itself ? Although SUBSECTION_SHIFT
> > might never reach the PUD level but this will help keep the flags calculations
> > bit simple and ready for all future changes.
> > 
> 
> I suppose that it's because these are significantly larger than 2M, whereas
> Catalin assumed SUBSECTION_SIZE would not increase?
> His comment:
> "should cover any changes to SUBSECTION_SHIFT making it *smaller* than 2MB.
> "

Yeah, I was thinking of having fewer code lines. Otherwise the compiler
would likely optimise them anyway to a single assignment.

-- 
Catalin