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Tue, 21 Jun 2022 20:31:24 -0700 (PDT) Date: Wed, 22 Jun 2022 11:31:21 +0800 From: Muchun Song To: Andrew Morton Cc: corbet@lwn.net, david@redhat.com, mike.kravetz@oracle.com, osalvador@suse.de, paulmck@kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, duanxiongchun@bytedance.com, smuchun@gmail.com Subject: Re: [PATCH v5 0/2] make hugetlb_optimize_vmemmap compatible with memmap_on_memory Message-ID: References: <20220620110616.12056-1-songmuchun@bytedance.com> <20220621135313.ae6fbc28338f1220328694f7@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220621135313.ae6fbc28338f1220328694f7@linux-foundation.org> ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1655868704; a=rsa-sha256; cv=none; b=GjeNQfS2SEHmNPs5hiogBMJ8XwLbqjvzqk7ZD+IrRefS951+0TVLJzeLKc14SoCtch2pUo zlX4Pc7a/GS/JyIaavxRByzG1l3oBYICqLmqIfJfCiUv8cKCbxXTjA3WY7l+KGLgvu6b1h YrxFRbOEcrU6668Dev4BPQ0ubVDlsyM= ARC-Authentication-Results: i=1; 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spf=pass (imf19.hostedemail.com: domain of songmuchun@bytedance.com designates 209.85.215.174 as permitted sender) smtp.mailfrom=songmuchun@bytedance.com; dmarc=pass (policy=none) header.from=bytedance.com X-Rspamd-Server: rspam08 X-Stat-Signature: bbb8b8s7i66jasqiqt8yktrezh8dwauq X-HE-Tag: 1655868698-497567 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 Tue, Jun 21, 2022 at 01:53:13PM -0700, Andrew Morton wrote: > On Mon, 20 Jun 2022 19:06:14 +0800 Muchun Song wrote: > > > This series makes hugetlb_optimize_vmemmap compatible with memmap_on_memory > > and is based on mm-stable. The reason refers to the patch 2's commit log. > > > > v5: > > - Replace enum to defines per David. > > - Walk vmemmap page tables to avoid false-positive. > > I can't see this second change in the v3->v5 deltas? > My changlog is not clear, Let me clarify it here. v3: Drop a section flag SECTION_CANNOT_OPTIMIZE_VMEMMAP and introduce a page flag PageVmemmapSelfHosted to make both parameters compatible. v4: Fix compiling error when !CONFIG_MEMORY_HOTPLUG and a bug when memory block spans multiple sections. v5: Fix a bug which PageVmemmapSelfHosted() check can be false-positive. Thanks. > From: Muchun Song > Subject: mm-memory_hotplug-enumerate-all-supported-section-flags-v5 > Date: Mon, 20 Jun 2022 19:06:15 +0800 > > replace enum with defines per David > > Link: https://lkml.kernel.org/r/20220620110616.12056-2-songmuchun@bytedance.com > Signed-off-by: Muchun Song > Signed-off-by: Andrew Morton > --- > > include/linux/mmzone.h | 13 +++++-------- > 1 file changed, 5 insertions(+), 8 deletions(-) > > --- a/include/linux/mmzone.h~mm-memory_hotplug-enumerate-all-supported-section-flags-v5 > +++ a/include/linux/mmzone.h > @@ -1439,16 +1439,13 @@ enum { > SECTION_MAP_LAST_BIT, > }; > > -enum { > - SECTION_MARKED_PRESENT = BIT(SECTION_MARKED_PRESENT_BIT), > - SECTION_HAS_MEM_MAP = BIT(SECTION_HAS_MEM_MAP_BIT), > - SECTION_IS_ONLINE = BIT(SECTION_IS_ONLINE_BIT), > - SECTION_IS_EARLY = BIT(SECTION_IS_EARLY_BIT), > +#define SECTION_MARKED_PRESENT BIT(SECTION_MARKED_PRESENT_BIT) > +#define SECTION_HAS_MEM_MAP BIT(SECTION_HAS_MEM_MAP_BIT) > +#define SECTION_IS_ONLINE BIT(SECTION_IS_ONLINE_BIT) > +#define SECTION_IS_EARLY BIT(SECTION_IS_EARLY_BIT) > #ifdef CONFIG_ZONE_DEVICE > - SECTION_TAINT_ZONE_DEVICE = BIT(SECTION_TAINT_ZONE_DEVICE_BIT), > +#define SECTION_TAINT_ZONE_DEVICE BIT(SECTION_TAINT_ZONE_DEVICE_BIT) > #endif > -}; > - > #define SECTION_MAP_MASK (~(BIT(SECTION_MAP_LAST_BIT) - 1)) > #define SECTION_NID_SHIFT SECTION_MAP_LAST_BIT > > _ > > > > > From: Muchun Song > Subject: mm-memory_hotplug-make-hugetlb_optimize_vmemmap-compatible-with-memmap_on_memory-v5 > Date: Mon, 20 Jun 2022 19:06:16 +0800 > > walk vmemmap page tables to avoid false-positive > > Link: https://lkml.kernel.org/r/20220620110616.12056-3-songmuchun@bytedance.com > Signed-off-by: Muchun Song > Co-developed-by: Oscar Salvador > Signed-off-by: Oscar Salvador > Signed-off-by: Andrew Morton > --- > > mm/hugetlb_vmemmap.c | 69 ++++++++++++++++++++++++++--------------- > 1 file changed, 44 insertions(+), 25 deletions(-) > > --- a/mm/hugetlb_vmemmap.c~mm-memory_hotplug-make-hugetlb_optimize_vmemmap-compatible-with-memmap_on_memory-v5 > +++ a/mm/hugetlb_vmemmap.c > @@ -10,6 +10,7 @@ > */ > #define pr_fmt(fmt) "HugeTLB: " fmt > > +#include > #include "hugetlb_vmemmap.h" > > /* > @@ -99,34 +100,52 @@ int hugetlb_vmemmap_alloc(struct hstate > static unsigned int vmemmap_optimizable_pages(struct hstate *h, > struct page *head) > { > - struct mem_section *ms; > - struct page *vmemmap_page; > - unsigned long pfn = page_to_pfn(head); > - > if (READ_ONCE(vmemmap_optimize_mode) == VMEMMAP_OPTIMIZE_OFF) > return 0; > > - ms = __pfn_to_section(pfn); > - vmemmap_page = sparse_decode_mem_map(ms->section_mem_map, > - pfn_to_section_nr(pfn)); > - /* > - * Only the vmemmap pages' vmemmap may be marked as VmemmapSelfHosted. > - * > - * Due to HugeTLB alignment requirements, and the vmemmap pages being > - * at the start of the hotplugged memory region. Checking any vmemmap > - * page's vmemmap is fine. > - * > - * [ hotplugged memory ] > - * [ vmemmap ][ usable memory ] > - * ^ | | | > - * +---+ | | > - * ^ | | > - * +--------+ | > - * ^ | > - * +-----------------+ > - */ > - if (PageVmemmapSelfHosted(vmemmap_page)) > - return 0; > + if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG)) { > + pmd_t *pmdp, pmd; > + struct page *vmemmap_page; > + unsigned long vaddr = (unsigned long)head; > + > + /* > + * Only the vmemmap page's vmemmap page can be self-hosted. > + * Walking the page tables to find the backing page of the > + * vmemmap page. > + */ > + pmdp = pmd_off_k(vaddr); > + /* > + * The READ_ONCE() is used to stabilize *pmdp in a register or > + * on the stack so that it will stop changing under the code. > + * The only concurrent operation where it can be changed is > + * split_vmemmap_huge_pmd() (*pmdp will be stable after this > + * operation). > + */ > + pmd = READ_ONCE(*pmdp); > + if (pmd_leaf(pmd)) > + vmemmap_page = pmd_page(pmd) + pte_index(vaddr); > + else > + vmemmap_page = pte_page(*pte_offset_kernel(pmdp, vaddr)); > + /* > + * Due to HugeTLB alignment requirements and the vmemmap pages > + * being at the start of the hotplugged memory region in > + * memory_hotplug.memmap_on_memory case. Checking any vmemmap > + * page's vmemmap page if it is marked as VmemmapSelfHosted is > + * sufficient. > + * > + * [ hotplugged memory ] > + * [ section ][...][ section ] > + * [ vmemmap ][ usable memory ] > + * ^ | | | > + * +---+ | | > + * ^ | | > + * +-------+ | > + * ^ | > + * +-------------------------------------------+ > + */ > + if (PageVmemmapSelfHosted(vmemmap_page)) > + return 0; > + } > > return hugetlb_optimize_vmemmap_pages(h); > } > _ > >