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Thu, 03 Apr 2025 09:44:32 -0400 X-MC-Unique: JIRrw_pwMbizmmVqlqLmrQ-1 X-Mimecast-MFC-AGG-ID: JIRrw_pwMbizmmVqlqLmrQ_1743687871 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 1F6F71954B36; Thu, 3 Apr 2025 13:44:31 +0000 (UTC) Received: from localhost (unknown [10.72.112.12]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id A6CE8192C7C3; Thu, 3 Apr 2025 13:44:29 +0000 (UTC) Date: Thu, 3 Apr 2025 21:44:14 +0800 From: Baoquan He To: Ingo Molnar Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, yanjun.zhu@linux.dev, x86@kernel.org Subject: Re: [PATCH v2 6/7] x86/mm: remove p4d_leaf definition Message-ID: References: <20250331081327.256412-1-bhe@redhat.com> <20250331081327.256412-7-bhe@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 X-Rspamd-Server: rspam01 X-Stat-Signature: xwxnb43oagy81j1x1auwn9yzjpe3ghwx X-Rspam-User: X-Rspamd-Queue-Id: D77DC4000E X-HE-Tag: 1743687877-378403 X-HE-Meta: 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 COEebpKF tjMGtNOprcPiD0UdZR1WiRjktF/ey/FPmTBhpKXpwQoihIvol1VghRJUETcFwV2RcqKao/qkUAmzxCqNy/ixamGQSx+gw2VmodkgUwpxyMklfgONXlNMW1Rn1zYyt3DXRThOG7gVCvFyBEgnWd8T+xc/Z89K4/Wgce8QuPbU8ewbq47V+MbWJrTdq3mglDEPd4Xix1pS8GOl8tKKExQUS1PHIXgpCouWlmWoTWDSl5StxqvgKYMVvPkEXrtGIViP/Qhz509O9oDGIgEuCRFtLGAPxU/+zE1z+SMSkbWiz+T9KeKOC5V/da4L7UCBe/x+1bkFosPD4qQm+4pCaKgnFV3M4NEdo+fIzA9isVdfJB10nh0FXoiw5baSFLAn0i6w32RzMQymrTTvYTv43lNDORSmhOvfc8iSbxMWmeB5bobK26Eg7IbFyInOU0wcW9Aeqg8+IRW2fds4FKt/tvFrj/J/1MA== 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: List-Subscribe: List-Unsubscribe: On 04/01/25 at 09:20am, Ingo Molnar wrote: > > * Baoquan He wrote: > > > > So the above comment should have said '256 TB' pages, unless > > > there's some naming weirdness I missed. > > > > Hmm, there could be misunderstanding here. In 5-level paging, PGD is > > the highest level, P4D is the next level of PGD. You may have > > reversed their order. > > Erm, yes indeed I flipped those two, so the correct table should be: > > - level 0: 4K pages > - level 1: 512x 4K = 2MB 'large' pages > - level 2: 512x 2MB = 1GB 'huge' pages > - level 3: 512x 1GB = 512GB 'P4D' pages > - level 4: 512x 512GB = 256TB 'PGD' pages > > I'm wondering whether 512GB pages will be called 'terapages'. ;-) Forgot replying to this one. With my understanding, MM usually don't name large page of different size a specific name, just call them hugepage + size, e.g 2M huge page, or 1G huge page. Sometime when we build mapping for them, we will call them PMD hugepage or PUD hugepage. I remember in x86 ARCH direct mapping is built with invocation of init_mem_mapping(), and the mapping to 2M or 1G directly is called large page mapping or PMD/PUD huge page mapping. They are similar. Hope other MM people can correct me if I am wrong.