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David Alan Gilbert" , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 04/26] hugetlb: make huge_pte_lockptr take an explicit shift argument. 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bh=zOW2bjWI4nmTuHstZl081QFDk/lt13dFqJ3SCVtfayg=; b=qe3kMOngkH/woIfS+30e5/RJxxybO4niheEjtpwBqHmbPb0b2d/FVcAZzO0KEJ0BpStYcA Ce1czmqkQM3KYTnbQi5TcTYpzYykPRPpkpWEG4Jad31T/SDy4Ce7kFvLUNkdQzhWvzEdez l4FyeRke2AiKSF7l4D2WfF9kRDH5v7E= X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 65FFF1C003C Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=oracle.com header.s=corp-2021-07-09 header.b=sCNQo3T2; dkim=pass header.d=oracle.onmicrosoft.com header.s=selector2-oracle-onmicrosoft-com header.b=O3o1XfRw; arc=pass ("microsoft.com:s=arcselector9901:i=1"); spf=none (imf20.hostedemail.com: domain of mike.kravetz@oracle.com has no SPF policy when checking 205.220.177.32) smtp.mailfrom=mike.kravetz@oracle.com; dmarc=pass (policy=none) header.from=oracle.com X-Rspam-User: X-Stat-Signature: 1qjswhnjt31hxi3uu1153krohbi14e9p X-HE-Tag: 1656363122-495116 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 06/24/22 17:36, James Houghton wrote: > This is needed to handle PTL locking with high-granularity mapping. We > won't always be using the PMD-level PTL even if we're using the 2M > hugepage hstate. It's possible that we're dealing with 4K PTEs, in which > case, we need to lock the PTL for the 4K PTE. I'm not really sure why this would be required. Why not use the PMD level lock for 4K PTEs? Seems that would scale better with less contention than using the more coarse mm lock. -- Mike Kravetz