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Tue, 24 Nov 2020 10:31:20 +0000 (UTC) Received: from DGGEMM402-HUB.china.huawei.com (unknown [172.30.72.56]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4CgKzx3Yjkz4xlG; Tue, 24 Nov 2020 18:30:53 +0800 (CST) Received: from dggemi761-chm.china.huawei.com (10.1.198.147) by DGGEMM402-HUB.china.huawei.com (10.3.20.210) with Microsoft SMTP Server (TLS) id 14.3.487.0; Tue, 24 Nov 2020 18:31:13 +0800 Received: from dggemi761-chm.china.huawei.com (10.1.198.147) by dggemi761-chm.china.huawei.com (10.1.198.147) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1913.5; Tue, 24 Nov 2020 18:31:12 +0800 Received: from dggemi761-chm.china.huawei.com ([10.9.49.202]) by dggemi761-chm.china.huawei.com ([10.9.49.202]) with mapi id 15.01.1913.007; Tue, 24 Nov 2020 18:31:12 +0800 From: "Song Bao Hua (Barry Song)" To: Oscar Salvador , Muchun Song CC: "corbet@lwn.net" , "mike.kravetz@oracle.com" , "tglx@linutronix.de" , "mingo@redhat.com" , "bp@alien8.de" , "x86@kernel.org" , "hpa@zytor.com" , "dave.hansen@linux.intel.com" , "luto@kernel.org" , "peterz@infradead.org" , "viro@zeniv.linux.org.uk" , "akpm@linux-foundation.org" , "paulmck@kernel.org" , "mchehab+huawei@kernel.org" , "pawan.kumar.gupta@linux.intel.com" , "rdunlap@infradead.org" , "oneukum@suse.com" , "anshuman.khandual@arm.com" , "jroedel@suse.de" , "almasrymina@google.com" , "rientjes@google.com" , "willy@infradead.org" , "mhocko@suse.com" , "duanxiongchun@bytedance.com" , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "linux-fsdevel@vger.kernel.org" Subject: RE: [PATCH v6 07/16] x86/mm/64: Disable PMD page mapping of vmemmap Thread-Topic: [PATCH v6 07/16] x86/mm/64: Disable PMD page mapping of vmemmap Thread-Index: AQHWwkhOPqtKcyIq80+fWoEXOrKJHKnWjWGAgACFgQA= Date: Tue, 24 Nov 2020 10:31:12 +0000 Message-ID: References: <20201124095259.58755-1-songmuchun@bytedance.com> <20201124095259.58755-8-songmuchun@bytedance.com> <20201124102441.GA24718@linux> In-Reply-To: <20201124102441.GA24718@linux> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.126.201.209] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-CFilter-Loop: Reflected 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: > -----Original Message----- > From: owner-linux-mm@kvack.org [mailto:owner-linux-mm@kvack.org] On > Behalf Of Oscar Salvador > Sent: Tuesday, November 24, 2020 11:25 PM > To: Muchun Song > Cc: corbet@lwn.net; mike.kravetz@oracle.com; tglx@linutronix.de; > mingo@redhat.com; bp@alien8.de; x86@kernel.org; hpa@zytor.com; > dave.hansen@linux.intel.com; luto@kernel.org; peterz@infradead.org; > viro@zeniv.linux.org.uk; akpm@linux-foundation.org; paulmck@kernel.org; > mchehab+huawei@kernel.org; pawan.kumar.gupta@linux.intel.com; > rdunlap@infradead.org; oneukum@suse.com; anshuman.khandual@arm.com; > jroedel@suse.de; almasrymina@google.com; rientjes@google.com; > willy@infradead.org; mhocko@suse.com; Song Bao Hua (Barry Song) > ; duanxiongchun@bytedance.com; > linux-doc@vger.kernel.org; linux-kernel@vger.kernel.org; linux-mm@kvack.o= rg; > linux-fsdevel@vger.kernel.org > Subject: Re: [PATCH v6 07/16] x86/mm/64: Disable PMD page mapping of > vmemmap >=20 > On Tue, Nov 24, 2020 at 05:52:50PM +0800, Muchun Song wrote: > > If we enable the CONFIG_HUGETLB_PAGE_FREE_VMEMMAP, we can just > > disbale PMD page mapping of vmemmap to simplify the code. In this > > case, we do not need complex code doing vmemmap page table > > manipulation. This is a way to simply the first version of this > > patch series. In the future, we can add some code doing page table > > manipulation. >=20 > IIRC, CONFIG_HUGETLB_PAGE_FREE_VMEMMAP was supposed to be enabled > by default, > right? > And we would control whether we __really__ want to this by a boot option, > which was disabled by default? >=20 > If you go for populating the memmap with basepages by checking > CONFIG_HUGETLB_PAGE_FREE_VMEMMAP, would not everybody, even the > ones that > did not enable this by the boot option be affected? >=20 I would believe we could only bypass the pmd mapping of vmemmap while free_vmemmap is explicitly enabled. pmd mapping shouldn't be disabled in default. Would a cmdline of enabling vmemmap_free be used for the first patchset? > -- > Oscar Salvador > SUSE L3 Thanks Barry