From: Joao Martins <joao.m.martins@oracle.com> To: Dan Williams <dan.j.williams@intel.com> Cc: Linux MM <linux-mm@kvack.org>, linux-nvdimm <linux-nvdimm@lists.01.org>, Matthew Wilcox <willy@infradead.org>, Jason Gunthorpe <jgg@ziepe.ca>, Muchun Song <songmuchun@bytedance.com>, Mike Kravetz <mike.kravetz@oracle.com>, Andrew Morton <akpm@linux-foundation.org> Subject: Re: [PATCH RFC 3/9] sparse-vmemmap: Reuse vmemmap areas for a given page size Date: Mon, 22 Feb 2021 11:42:28 +0000 [thread overview] Message-ID: <621ff98b-cb75-e4d7-8f09-882cb2b984d2@oracle.com> (raw) In-Reply-To: <CAPcyv4ixD6_KEpuXkpeH6JNLvoahch8rm8J55o1B97ghrtcbjQ@mail.gmail.com> On 2/20/21 3:34 AM, Dan Williams wrote: > On Tue, Dec 8, 2020 at 9:32 AM Joao Martins <joao.m.martins@oracle.com> wrote: >> >> Introduce a new flag, MEMHP_REUSE_VMEMMAP, which signals that >> struct pages are onlined with a given alignment, and should reuse the >> tail pages vmemmap areas. On that circunstamce we reuse the PFN backing > > s/On that circunstamce we reuse/Reuse/ > > Kills a "we" and switches to imperative tense. I noticed a couple > other "we"s in the previous patches, but this crossed my threshold to > make a comment. > /me nods. Will fix. >> only the tail pages subsections, while letting the head page PFN remain >> different. This presumes that the backing page structs are compound >> pages, such as the case for compound pagemaps (i.e. ZONE_DEVICE with >> PGMAP_COMPOUND set) >> >> On 2M compound pagemaps, it lets us save 6 pages out of the 8 necessary > > s/lets us save/saves/ > Will fix. >> PFNs necessary > > s/8 necessary PFNs necessary/8 PFNs necessary/ Will fix. > >> to describe the subsection's 32K struct pages we are >> onlining. > > s/we are onlining/being mapped/ > > ...because ZONE_DEVICE pages are never "onlined". > >> On a 1G compound pagemap it let us save 4096 pages. > > s/lets us save/saves/ > Will fix both. >> >> Sections are 128M (or bigger/smaller), > > Huh? > Section size is arch-dependent if we are being hollistic. On x86 it's 64M, 128M or 512M right? #ifdef CONFIG_X86_32 # ifdef CONFIG_X86_PAE # define SECTION_SIZE_BITS 29 # define MAX_PHYSMEM_BITS 36 # else # define SECTION_SIZE_BITS 26 # define MAX_PHYSMEM_BITS 32 # endif #else /* CONFIG_X86_32 */ # define SECTION_SIZE_BITS 27 /* matt - 128 is convenient right now */ # define MAX_PHYSMEM_BITS (pgtable_l5_enabled() ? 52 : 46) #endif Also, me pointing about section sizes, is because a 1GB+ page vmemmap population will cross sections in how sparsemem populates the vmemmap. And on that case we gotta reuse the the PTE/PMD pages across multiple invocations of vmemmap_populate_basepages(). Either that, or looking at the previous page PTE, but that might be ineficient. >> @@ -229,38 +235,95 @@ int __meminit vmemmap_populate_basepages(unsigned long start, unsigned long end, >> for (; addr < end; addr += PAGE_SIZE) { >> pgd = vmemmap_pgd_populate(addr, node); >> if (!pgd) >> - return -ENOMEM; >> + return NULL; >> p4d = vmemmap_p4d_populate(pgd, addr, node); >> if (!p4d) >> - return -ENOMEM; >> + return NULL; >> pud = vmemmap_pud_populate(p4d, addr, node); >> if (!pud) >> - return -ENOMEM; >> + return NULL; >> pmd = vmemmap_pmd_populate(pud, addr, node); >> if (!pmd) >> - return -ENOMEM; >> - pte = vmemmap_pte_populate(pmd, addr, node, altmap); >> + return NULL; >> + pte = vmemmap_pte_populate(pmd, addr, node, altmap, block); >> if (!pte) >> - return -ENOMEM; >> + return NULL; >> vmemmap_verify(pte, node, addr, addr + PAGE_SIZE); >> } >> >> + return __va(__pfn_to_phys(pte_pfn(*pte))); >> +} >> + >> +int __meminit vmemmap_populate_basepages(unsigned long start, unsigned long end, >> + int node, struct vmem_altmap *altmap) >> +{ >> + if (!__vmemmap_populate_basepages(start, end, node, altmap, NULL)) >> + return -ENOMEM; >> return 0; >> } >> >> +static struct page * __meminit vmemmap_populate_reuse(unsigned long start, >> + unsigned long end, int node, >> + struct vmem_context *ctx) >> +{ >> + unsigned long size, addr = start; >> + unsigned long psize = PHYS_PFN(ctx->align) * sizeof(struct page); >> + >> + size = min(psize, end - start); >> + >> + for (; addr < end; addr += size) { >> + unsigned long head = addr + PAGE_SIZE; >> + unsigned long tail = addr; >> + unsigned long last = addr + size; >> + void *area; >> + >> + if (ctx->block_page && >> + IS_ALIGNED((addr - ctx->block_page), psize)) >> + ctx->block = NULL; >> + >> + area = ctx->block; >> + if (!area) { >> + if (!__vmemmap_populate_basepages(addr, head, node, >> + ctx->altmap, NULL)) >> + return NULL; >> + >> + tail = head + PAGE_SIZE; >> + area = __vmemmap_populate_basepages(head, tail, node, >> + ctx->altmap, NULL); >> + if (!area) >> + return NULL; >> + >> + ctx->block = area; >> + ctx->block_page = addr; >> + } >> + >> + if (!__vmemmap_populate_basepages(tail, last, node, >> + ctx->altmap, area)) >> + return NULL; >> + } > > I think that compound page accounting and combined altmap accounting > makes this difficult to read, and I think the compound page case > deserves it's own first class loop rather than reusing > vmemmap_populate_basepages(). With the suggestion to drop altmap > support I'd expect a vmmemap_populate_compound that takes a compound > page size and goes the right think with respect to mapping all the > tail pages to the same pfn. > I can move this to a separate loop as suggested. But to be able to map all tail pages in one call of vmemmap_populate_compound() this might requires changes in sparsemem generic code that I am not so sure they are warranted the added complexity. Otherwise I'll have to probably keep this logic of @ctx to be able to pass the page to be reused (i.e. @block and @block_page). That's actually the main reason that made me introduce a struct vmem_context. _______________________________________________ Linux-nvdimm mailing list -- linux-nvdimm@lists.01.org To unsubscribe send an email to linux-nvdimm-leave@lists.01.org
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From: Joao Martins <joao.m.martins@oracle.com> To: Dan Williams <dan.j.williams@intel.com> Cc: Linux MM <linux-mm@kvack.org>, Ira Weiny <ira.weiny@intel.com>, linux-nvdimm <linux-nvdimm@lists.01.org>, Matthew Wilcox <willy@infradead.org>, Jason Gunthorpe <jgg@ziepe.ca>, Jane Chu <jane.chu@oracle.com>, Muchun Song <songmuchun@bytedance.com>, Mike Kravetz <mike.kravetz@oracle.com>, Andrew Morton <akpm@linux-foundation.org> Subject: Re: [PATCH RFC 3/9] sparse-vmemmap: Reuse vmemmap areas for a given page size Date: Mon, 22 Feb 2021 11:42:28 +0000 [thread overview] Message-ID: <621ff98b-cb75-e4d7-8f09-882cb2b984d2@oracle.com> (raw) In-Reply-To: <CAPcyv4ixD6_KEpuXkpeH6JNLvoahch8rm8J55o1B97ghrtcbjQ@mail.gmail.com> On 2/20/21 3:34 AM, Dan Williams wrote: > On Tue, Dec 8, 2020 at 9:32 AM Joao Martins <joao.m.martins@oracle.com> wrote: >> >> Introduce a new flag, MEMHP_REUSE_VMEMMAP, which signals that >> struct pages are onlined with a given alignment, and should reuse the >> tail pages vmemmap areas. On that circunstamce we reuse the PFN backing > > s/On that circunstamce we reuse/Reuse/ > > Kills a "we" and switches to imperative tense. I noticed a couple > other "we"s in the previous patches, but this crossed my threshold to > make a comment. > /me nods. Will fix. >> only the tail pages subsections, while letting the head page PFN remain >> different. This presumes that the backing page structs are compound >> pages, such as the case for compound pagemaps (i.e. ZONE_DEVICE with >> PGMAP_COMPOUND set) >> >> On 2M compound pagemaps, it lets us save 6 pages out of the 8 necessary > > s/lets us save/saves/ > Will fix. >> PFNs necessary > > s/8 necessary PFNs necessary/8 PFNs necessary/ Will fix. > >> to describe the subsection's 32K struct pages we are >> onlining. > > s/we are onlining/being mapped/ > > ...because ZONE_DEVICE pages are never "onlined". > >> On a 1G compound pagemap it let us save 4096 pages. > > s/lets us save/saves/ > Will fix both. >> >> Sections are 128M (or bigger/smaller), > > Huh? > Section size is arch-dependent if we are being hollistic. On x86 it's 64M, 128M or 512M right? #ifdef CONFIG_X86_32 # ifdef CONFIG_X86_PAE # define SECTION_SIZE_BITS 29 # define MAX_PHYSMEM_BITS 36 # else # define SECTION_SIZE_BITS 26 # define MAX_PHYSMEM_BITS 32 # endif #else /* CONFIG_X86_32 */ # define SECTION_SIZE_BITS 27 /* matt - 128 is convenient right now */ # define MAX_PHYSMEM_BITS (pgtable_l5_enabled() ? 52 : 46) #endif Also, me pointing about section sizes, is because a 1GB+ page vmemmap population will cross sections in how sparsemem populates the vmemmap. And on that case we gotta reuse the the PTE/PMD pages across multiple invocations of vmemmap_populate_basepages(). Either that, or looking at the previous page PTE, but that might be ineficient. >> @@ -229,38 +235,95 @@ int __meminit vmemmap_populate_basepages(unsigned long start, unsigned long end, >> for (; addr < end; addr += PAGE_SIZE) { >> pgd = vmemmap_pgd_populate(addr, node); >> if (!pgd) >> - return -ENOMEM; >> + return NULL; >> p4d = vmemmap_p4d_populate(pgd, addr, node); >> if (!p4d) >> - return -ENOMEM; >> + return NULL; >> pud = vmemmap_pud_populate(p4d, addr, node); >> if (!pud) >> - return -ENOMEM; >> + return NULL; >> pmd = vmemmap_pmd_populate(pud, addr, node); >> if (!pmd) >> - return -ENOMEM; >> - pte = vmemmap_pte_populate(pmd, addr, node, altmap); >> + return NULL; >> + pte = vmemmap_pte_populate(pmd, addr, node, altmap, block); >> if (!pte) >> - return -ENOMEM; >> + return NULL; >> vmemmap_verify(pte, node, addr, addr + PAGE_SIZE); >> } >> >> + return __va(__pfn_to_phys(pte_pfn(*pte))); >> +} >> + >> +int __meminit vmemmap_populate_basepages(unsigned long start, unsigned long end, >> + int node, struct vmem_altmap *altmap) >> +{ >> + if (!__vmemmap_populate_basepages(start, end, node, altmap, NULL)) >> + return -ENOMEM; >> return 0; >> } >> >> +static struct page * __meminit vmemmap_populate_reuse(unsigned long start, >> + unsigned long end, int node, >> + struct vmem_context *ctx) >> +{ >> + unsigned long size, addr = start; >> + unsigned long psize = PHYS_PFN(ctx->align) * sizeof(struct page); >> + >> + size = min(psize, end - start); >> + >> + for (; addr < end; addr += size) { >> + unsigned long head = addr + PAGE_SIZE; >> + unsigned long tail = addr; >> + unsigned long last = addr + size; >> + void *area; >> + >> + if (ctx->block_page && >> + IS_ALIGNED((addr - ctx->block_page), psize)) >> + ctx->block = NULL; >> + >> + area = ctx->block; >> + if (!area) { >> + if (!__vmemmap_populate_basepages(addr, head, node, >> + ctx->altmap, NULL)) >> + return NULL; >> + >> + tail = head + PAGE_SIZE; >> + area = __vmemmap_populate_basepages(head, tail, node, >> + ctx->altmap, NULL); >> + if (!area) >> + return NULL; >> + >> + ctx->block = area; >> + ctx->block_page = addr; >> + } >> + >> + if (!__vmemmap_populate_basepages(tail, last, node, >> + ctx->altmap, area)) >> + return NULL; >> + } > > I think that compound page accounting and combined altmap accounting > makes this difficult to read, and I think the compound page case > deserves it's own first class loop rather than reusing > vmemmap_populate_basepages(). With the suggestion to drop altmap > support I'd expect a vmmemap_populate_compound that takes a compound > page size and goes the right think with respect to mapping all the > tail pages to the same pfn. > I can move this to a separate loop as suggested. But to be able to map all tail pages in one call of vmemmap_populate_compound() this might requires changes in sparsemem generic code that I am not so sure they are warranted the added complexity. Otherwise I'll have to probably keep this logic of @ctx to be able to pass the page to be reused (i.e. @block and @block_page). That's actually the main reason that made me introduce a struct vmem_context.
next prev parent reply other threads:[~2021-02-22 11:42 UTC|newest] Thread overview: 147+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-12-08 17:28 [PATCH RFC 0/9] mm, sparse-vmemmap: Introduce compound pagemaps Joao Martins 2020-12-08 17:28 ` Joao Martins 2020-12-08 17:28 ` [PATCH RFC 1/9] memremap: add ZONE_DEVICE support for compound pages Joao Martins 2020-12-08 17:28 ` Joao Martins 2020-12-09 5:59 ` John Hubbard 2020-12-09 5:59 ` John Hubbard 2020-12-09 6:33 ` Matthew Wilcox 2020-12-09 6:33 ` Matthew Wilcox 2020-12-09 13:12 ` Joao Martins 2020-12-09 13:12 ` Joao Martins 2021-02-20 1:43 ` Dan Williams 2021-02-20 1:43 ` Dan Williams 2021-02-22 11:24 ` Joao Martins 2021-02-22 11:24 ` Joao Martins 2021-02-22 20:37 ` Dan Williams 2021-02-22 20:37 ` Dan Williams 2021-02-23 15:46 ` Joao Martins 2021-02-23 15:46 ` Joao Martins 2021-02-23 16:50 ` Dan Williams 2021-02-23 16:50 ` Dan Williams 2021-02-23 17:18 ` Joao Martins 2021-02-23 17:18 ` Joao Martins 2021-02-23 18:18 ` Dan Williams 2021-02-23 18:18 ` Dan Williams 2021-03-10 18:12 ` Joao Martins 2021-03-10 18:12 ` Joao Martins 2021-03-12 5:54 ` Dan Williams 2021-03-12 5:54 ` Dan Williams 2021-02-20 1:24 ` Dan Williams 2021-02-20 1:24 ` Dan Williams 2021-02-22 11:09 ` Joao Martins 2021-02-22 11:09 ` Joao Martins 2020-12-08 17:28 ` [PATCH RFC 2/9] sparse-vmemmap: Consolidate arguments in vmemmap section populate Joao Martins 2020-12-08 17:28 ` Joao Martins 2020-12-09 6:16 ` John Hubbard 2020-12-09 6:16 ` John Hubbard 2020-12-09 13:51 ` Joao Martins 2020-12-09 13:51 ` Joao Martins 2021-02-20 1:49 ` Dan Williams 2021-02-20 1:49 ` Dan Williams 2021-02-22 11:26 ` Joao Martins 2021-02-22 11:26 ` Joao Martins 2020-12-08 17:28 ` [PATCH RFC 3/9] sparse-vmemmap: Reuse vmemmap areas for a given mhp_params::align Joao Martins 2020-12-08 17:28 ` Joao Martins 2020-12-08 17:38 ` Joao Martins 2020-12-08 17:38 ` Joao Martins 2020-12-08 17:28 ` [PATCH RFC 3/9] sparse-vmemmap: Reuse vmemmap areas for a given page size Joao Martins 2020-12-08 17:28 ` Joao Martins 2021-02-20 3:34 ` Dan Williams 2021-02-20 3:34 ` Dan Williams 2021-02-22 11:42 ` Joao Martins [this message] 2021-02-22 11:42 ` Joao Martins 2021-02-22 22:40 ` Dan Williams 2021-02-22 22:40 ` Dan Williams 2021-02-23 15:46 ` Joao Martins 2021-02-23 15:46 ` Joao Martins 2020-12-08 17:28 ` [PATCH RFC 4/9] mm/page_alloc: Reuse tail struct pages for compound pagemaps Joao Martins 2020-12-08 17:28 ` Joao Martins 2021-02-20 6:17 ` Dan Williams 2021-02-20 6:17 ` Dan Williams 2021-02-22 12:01 ` Joao Martins 2021-02-22 12:01 ` Joao Martins 2020-12-08 17:28 ` [PATCH RFC 5/9] device-dax: Compound pagemap support Joao Martins 2020-12-08 17:28 ` Joao Martins 2020-12-08 17:28 ` [PATCH RFC 6/9] mm/gup: Grab head page refcount once for group of subpages Joao Martins 2020-12-08 17:28 ` Joao Martins 2020-12-08 19:49 ` Jason Gunthorpe 2020-12-09 11:05 ` Joao Martins 2020-12-09 11:05 ` Joao Martins 2020-12-09 15:15 ` Jason Gunthorpe 2020-12-09 16:02 ` Joao Martins 2020-12-09 16:02 ` Joao Martins 2020-12-09 16:24 ` Jason Gunthorpe 2020-12-09 17:27 ` Joao Martins 2020-12-09 17:27 ` Joao Martins 2020-12-09 18:14 ` Matthew Wilcox 2020-12-09 18:14 ` Matthew Wilcox 2020-12-09 19:08 ` Jason Gunthorpe 2020-12-10 15:43 ` Joao Martins 2020-12-10 15:43 ` Joao Martins 2020-12-09 4:40 ` John Hubbard 2020-12-09 4:40 ` John Hubbard 2020-12-09 13:44 ` Joao Martins 2020-12-09 13:44 ` Joao Martins 2020-12-08 17:28 ` [PATCH RFC 7/9] mm/gup: Decrement head page " Joao Martins 2020-12-08 17:28 ` Joao Martins 2020-12-08 19:34 ` Jason Gunthorpe 2020-12-09 5:06 ` John Hubbard 2020-12-09 5:06 ` John Hubbard 2020-12-09 13:43 ` Jason Gunthorpe 2020-12-09 12:17 ` Joao Martins 2020-12-09 12:17 ` Joao Martins 2020-12-17 19:05 ` Joao Martins 2020-12-17 19:05 ` Joao Martins 2020-12-17 20:05 ` Jason Gunthorpe 2020-12-17 22:34 ` Joao Martins 2020-12-17 22:34 ` Joao Martins 2020-12-18 14:25 ` Jason Gunthorpe 2020-12-19 2:06 ` John Hubbard 2020-12-19 2:06 ` John Hubbard 2020-12-19 13:10 ` Joao Martins 2020-12-19 13:10 ` Joao Martins 2020-12-08 17:29 ` [PATCH RFC 8/9] RDMA/umem: batch page unpin in __ib_mem_release() Joao Martins 2020-12-08 17:29 ` Joao Martins 2020-12-08 19:29 ` Jason Gunthorpe 2020-12-09 10:59 ` Joao Martins 2020-12-09 10:59 ` Joao Martins 2020-12-19 13:15 ` Joao Martins 2020-12-19 13:15 ` Joao Martins 2020-12-09 5:18 ` John Hubbard 2020-12-09 5:18 ` John Hubbard 2020-12-08 17:29 ` [PATCH RFC 9/9] mm: Add follow_devmap_page() for devdax vmas Joao Martins 2020-12-08 17:29 ` Joao Martins 2020-12-08 19:57 ` Jason Gunthorpe 2020-12-09 8:05 ` Christoph Hellwig 2020-12-09 8:05 ` Christoph Hellwig 2020-12-09 11:19 ` Joao Martins 2020-12-09 11:19 ` Joao Martins 2020-12-09 5:23 ` John Hubbard 2020-12-09 5:23 ` John Hubbard 2020-12-09 9:38 ` [PATCH RFC 0/9] mm, sparse-vmemmap: Introduce compound pagemaps David Hildenbrand 2020-12-09 9:38 ` David Hildenbrand 2020-12-09 9:52 ` [External] " Muchun Song 2020-12-09 9:52 ` Muchun Song 2021-02-20 1:18 ` Dan Williams 2021-02-20 1:18 ` Dan Williams 2021-02-22 11:06 ` Joao Martins 2021-02-22 11:06 ` Joao Martins 2021-02-22 14:32 ` Joao Martins 2021-02-22 14:32 ` Joao Martins 2021-02-23 16:28 ` Joao Martins 2021-02-23 16:28 ` Joao Martins 2021-02-23 16:44 ` Dan Williams 2021-02-23 16:44 ` Dan Williams 2021-02-23 17:15 ` Joao Martins 2021-02-23 17:15 ` Joao Martins 2021-02-23 18:15 ` Dan Williams 2021-02-23 18:15 ` Dan Williams 2021-02-23 18:54 ` Jason Gunthorpe 2021-02-23 22:48 ` Dan Williams 2021-02-23 22:48 ` Dan Williams 2021-02-23 23:07 ` Jason Gunthorpe 2021-02-24 0:14 ` Dan Williams 2021-02-24 0:14 ` Dan Williams 2021-02-24 1:00 ` Jason Gunthorpe 2021-02-24 1:32 ` Dan Williams 2021-02-24 1:32 ` Dan Williams
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