From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
To: "Jérôme Glisse" <jglisse@redhat.com>,
akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org
Cc: "John Hubbard" <jhubbard@nvidia.com>,
"Jérôme Glisse" <jglisse@redhat.com>,
"Jatin Kumar" <jakumar@nvidia.com>,
"Mark Hairgrove" <mhairgrove@nvidia.com>,
"Sherry Cheung" <SCheung@nvidia.com>,
"Subhash Gutti" <sgutti@nvidia.com>
Subject: Re: [HMM v13 16/18] mm/hmm/migrate: new memory migration helper for use with device memory
Date: Sat, 19 Nov 2016 01:27:28 +0530 [thread overview]
Message-ID: <87k2c0muhj.fsf@linux.vnet.ibm.com> (raw)
In-Reply-To: <1479493107-982-17-git-send-email-jglisse@redhat.com>
Jérôme Glisse <jglisse@redhat.com> writes:
> This patch add a new memory migration helpers, which migrate memory
> backing a range of virtual address of a process to different memory
> (which can be allocated through special allocator). It differs from
> numa migration by working on a range of virtual address and thus by
> doing migration in chunk that can be large enough to use DMA engine
> or special copy offloading engine.
>
> Expected users are any one with heterogeneous memory where different
> memory have different characteristics (latency, bandwidth, ...). As
> an example IBM platform with CAPI bus can make use of this feature
> to migrate between regular memory and CAPI device memory. New CPU
> architecture with a pool of high performance memory not manage as
> cache but presented as regular memory (while being faster and with
> lower latency than DDR) will also be prime user of this patch.
>
> Migration to private device memory will be usefull for device that
> have large pool of such like GPU, NVidia plans to use HMM for that.
>
..............
>+
> +static int hmm_collect_walk_pmd(pmd_t *pmdp,
> + unsigned long start,
> + unsigned long end,
> + struct mm_walk *walk)
> +{
> + struct hmm_migrate *migrate = walk->private;
> + struct mm_struct *mm = walk->vma->vm_mm;
> + unsigned long addr = start;
> + spinlock_t *ptl;
> + hmm_pfn_t *pfns;
> + int pages = 0;
> + pte_t *ptep;
> +
> +again:
> + if (pmd_none(*pmdp))
> + return 0;
> +
> + split_huge_pmd(walk->vma, pmdp, addr);
> + if (pmd_trans_unstable(pmdp))
> + goto again;
> +
> + pfns = &migrate->pfns[(addr - migrate->start) >> PAGE_SHIFT];
> + ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
> + arch_enter_lazy_mmu_mode();
> +
> + for (; addr < end; addr += PAGE_SIZE, pfns++, ptep++) {
> + unsigned long pfn;
> + swp_entry_t entry;
> + struct page *page;
> + hmm_pfn_t flags;
> + bool write;
> + pte_t pte;
> +
> + pte = ptep_get_and_clear(mm, addr, ptep);
> + if (!pte_present(pte)) {
> + if (pte_none(pte))
> + continue;
> +
> + entry = pte_to_swp_entry(pte);
> + if (!is_device_entry(entry)) {
> + set_pte_at(mm, addr, ptep, pte);
> + continue;
> + }
> +
> + flags = HMM_PFN_DEVICE | HMM_PFN_UNADDRESSABLE;
> + page = device_entry_to_page(entry);
> + write = is_write_device_entry(entry);
> + pfn = page_to_pfn(page);
> +
> + if (!(page->pgmap->flags & MEMORY_MOVABLE)) {
> + set_pte_at(mm, addr, ptep, pte);
> + continue;
> + }
> +
> + } else {
> + pfn = pte_pfn(pte);
> + page = pfn_to_page(pfn);
> + write = pte_write(pte);
> + flags = is_zone_device_page(page) ? HMM_PFN_DEVICE : 0;
> + }
> +
> + /* FIXME support THP see hmm_migrate_page_check() */
> + if (PageTransCompound(page))
> + continue;
> +
> + *pfns = hmm_pfn_from_pfn(pfn) | HMM_PFN_MIGRATE | flags;
> + *pfns |= write ? HMM_PFN_WRITE : 0;
> + migrate->npages++;
> + get_page(page);
> +
> + if (!trylock_page(page)) {
> + set_pte_at(mm, addr, ptep, pte);
> + } else {
> + pte_t swp_pte;
> +
> + *pfns |= HMM_PFN_LOCKED;
> +
> + entry = make_migration_entry(page, write);
> + swp_pte = swp_entry_to_pte(entry);
> + if (pte_soft_dirty(pte))
> + swp_pte = pte_swp_mksoft_dirty(swp_pte);
> + set_pte_at(mm, addr, ptep, swp_pte);
> +
> + page_remove_rmap(page, false);
> + put_page(page);
> + pages++;
> + }
Can you explain this. What does a failure to lock means here. Also why
convert the pte to migration entries here ? We do that in try_to_unmap right ?
> + }
> +
> + arch_leave_lazy_mmu_mode();
> + pte_unmap_unlock(ptep - 1, ptl);
> +
> + /* Only flush the TLB if we actually modified any entries */
> + if (pages)
> + flush_tlb_range(walk->vma, start, end);
> +
> + return 0;
> +}
>
next prev parent reply other threads:[~2016-11-18 19:57 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-18 18:18 [HMM v13 00/18] HMM (Heterogeneous Memory Management) v13 Jérôme Glisse
2016-11-18 18:18 ` [HMM v13 01/18] mm/memory/hotplug: convert device parameter bool to set of flags Jérôme Glisse
2016-11-21 0:44 ` Balbir Singh
2016-11-21 4:53 ` Jerome Glisse
2016-11-21 6:57 ` Anshuman Khandual
2016-11-21 12:19 ` Jerome Glisse
2016-11-21 6:41 ` Anshuman Khandual
2016-11-21 12:27 ` Jerome Glisse
2016-11-22 5:35 ` Anshuman Khandual
2016-11-22 14:08 ` Jerome Glisse
2016-11-18 18:18 ` [HMM v13 02/18] mm/ZONE_DEVICE/unaddressable: add support for un-addressable device memory Jérôme Glisse
2016-11-21 8:06 ` Anshuman Khandual
2016-11-21 12:33 ` Jerome Glisse
2016-11-22 5:15 ` Anshuman Khandual
2016-11-18 18:18 ` [HMM v13 03/18] mm/ZONE_DEVICE/free_hot_cold_page: catch ZONE_DEVICE pages Jérôme Glisse
2016-11-21 8:18 ` Anshuman Khandual
2016-11-21 12:50 ` Jerome Glisse
2016-11-22 4:30 ` Anshuman Khandual
2016-11-18 18:18 ` [HMM v13 04/18] mm/ZONE_DEVICE/free-page: callback when page is freed Jérôme Glisse
2016-11-21 1:49 ` Balbir Singh
2016-11-21 4:57 ` Jerome Glisse
2016-11-21 8:26 ` Anshuman Khandual
2016-11-21 12:34 ` Jerome Glisse
2016-11-22 5:02 ` Anshuman Khandual
2016-11-18 18:18 ` [HMM v13 05/18] mm/ZONE_DEVICE/devmem_pages_remove: allow early removal of device memory Jérôme Glisse
2016-11-21 10:37 ` Anshuman Khandual
2016-11-21 12:39 ` Jerome Glisse
2016-11-22 4:54 ` Anshuman Khandual
2016-11-18 18:18 ` [HMM v13 06/18] mm/ZONE_DEVICE/unaddressable: add special swap for unaddressable Jérôme Glisse
2016-11-21 2:06 ` Balbir Singh
2016-11-21 5:05 ` Jerome Glisse
2016-11-22 2:19 ` Balbir Singh
2016-11-22 13:59 ` Jerome Glisse
2016-11-21 11:10 ` Anshuman Khandual
2016-11-21 10:58 ` Anshuman Khandual
2016-11-21 12:42 ` Jerome Glisse
2016-11-22 4:48 ` Anshuman Khandual
2016-11-24 13:56 ` Jerome Glisse
2016-11-18 18:18 ` [HMM v13 07/18] mm/ZONE_DEVICE/x86: add support for un-addressable device memory Jérôme Glisse
2016-11-21 2:08 ` Balbir Singh
2016-11-21 5:08 ` Jerome Glisse
2016-11-18 18:18 ` [HMM v13 08/18] mm/hmm: heterogeneous memory management (HMM for short) Jérôme Glisse
2016-11-21 2:29 ` Balbir Singh
2016-11-21 5:14 ` Jerome Glisse
2016-11-23 4:03 ` Anshuman Khandual
2016-11-27 13:10 ` Jerome Glisse
2016-11-28 2:58 ` Anshuman Khandual
2016-11-28 9:41 ` Jerome Glisse
2016-11-18 18:18 ` [HMM v13 09/18] mm/hmm/mirror: mirror process address space on device with HMM helpers Jérôme Glisse
2016-11-21 2:42 ` Balbir Singh
2016-11-21 5:18 ` Jerome Glisse
2016-11-18 18:18 ` [HMM v13 10/18] mm/hmm/mirror: add range lock helper, prevent CPU page table update for the range Jérôme Glisse
2016-11-18 18:18 ` [HMM v13 11/18] mm/hmm/mirror: add range monitor helper, to monitor CPU page table update Jérôme Glisse
2016-11-18 18:18 ` [HMM v13 12/18] mm/hmm/mirror: helper to snapshot CPU page table Jérôme Glisse
2016-11-18 18:18 ` [HMM v13 13/18] mm/hmm/mirror: device page fault handler Jérôme Glisse
2016-11-18 18:18 ` [HMM v13 14/18] mm/hmm/migrate: support un-addressable ZONE_DEVICE page in migration Jérôme Glisse
2016-11-18 18:18 ` [HMM v13 15/18] mm/hmm/migrate: add new boolean copy flag to migratepage() callback Jérôme Glisse
2016-11-18 18:18 ` [HMM v13 16/18] mm/hmm/migrate: new memory migration helper for use with device memory Jérôme Glisse
2016-11-18 19:57 ` Aneesh Kumar K.V [this message]
2016-11-18 20:15 ` Jerome Glisse
2016-11-19 14:32 ` Aneesh Kumar K.V
2016-11-19 17:17 ` Jerome Glisse
2016-11-20 18:21 ` Aneesh Kumar K.V
2016-11-20 20:06 ` Jerome Glisse
2016-11-21 3:30 ` Balbir Singh
2016-11-21 5:31 ` Jerome Glisse
2016-11-18 18:18 ` [HMM v13 17/18] mm/hmm/devmem: device driver helper to hotplug ZONE_DEVICE memory Jérôme Glisse
2016-11-18 18:18 ` [HMM v13 18/18] mm/hmm/devmem: dummy HMM device as an helper for " Jérôme Glisse
2016-11-19 0:41 ` [HMM v13 00/18] HMM (Heterogeneous Memory Management) v13 John Hubbard
2016-11-19 14:50 ` Aneesh Kumar K.V
2016-11-23 9:16 ` Haggai Eran
2016-11-25 16:16 ` Jerome Glisse
2016-11-27 13:27 ` Haggai Eran
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