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authorDave Jiang <dave.jiang@intel.com>2017-02-24 14:56:59 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2017-02-24 17:46:54 -0800
commita2d581675d485eb7188f521f36efc114639a3096 (patch)
treeae566f77b965fed344458698fe6bb01280558647 /mm/memory.c
parentbd233f538d51c2cae6f0bfc2cf7f0960e1683b8a (diff)
mm,fs,dax: change ->pmd_fault to ->huge_fault
Patch series "1G transparent hugepage support for device dax", v2. The following series implements support for 1G trasparent hugepage on x86 for device dax. The bulk of the code was written by Mathew Wilcox a while back supporting transparent 1G hugepage for fs DAX. I have forward ported the relevant bits to 4.10-rc. The current submission has only the necessary code to support device DAX. Comments from Dan Williams: So the motivation and intended user of this functionality mirrors the motivation and users of 1GB page support in hugetlbfs. Given expected capacities of persistent memory devices an in-memory database may want to reduce tlb pressure beyond what they can already achieve with 2MB mappings of a device-dax file. We have customer feedback to that effect as Willy mentioned in his previous version of these patches [1]. [1]: https://lkml.org/lkml/2016/1/31/52 Comments from Nilesh @ Oracle: There are applications which have a process model; and if you assume 10,000 processes attempting to mmap all the 6TB memory available on a server; we are looking at the following: processes : 10,000 memory : 6TB pte @ 4k page size: 8 bytes / 4K of memory * #processes = 6TB / 4k * 8 * 10000 = 1.5GB * 80000 = 120,000GB pmd @ 2M page size: 120,000 / 512 = ~240GB pud @ 1G page size: 240GB / 512 = ~480MB As you can see with 2M pages, this system will use up an exorbitant amount of DRAM to hold the page tables; but the 1G pages finally brings it down to a reasonable level. Memory sizes will keep increasing; so this number will keep increasing. An argument can be made to convert the applications from process model to thread model, but in the real world that may not be always practical. Hopefully this helps explain the use case where this is valuable. This patch (of 3): In preparation for adding the ability to handle PUD pages, convert vm_operations_struct.pmd_fault to vm_operations_struct.huge_fault. The vm_fault structure is extended to include a union of the different page table pointers that may be needed, and three flag bits are reserved to indicate which type of pointer is in the union. [ross.zwisler@linux.intel.com: remove unused function ext4_dax_huge_fault()] Link: http://lkml.kernel.org/r/1485813172-7284-1-git-send-email-ross.zwisler@linux.intel.com [dave.jiang@intel.com: clear PMD or PUD size flags when in fall through path] Link: http://lkml.kernel.org/r/148589842696.5820.16078080610311444794.stgit@djiang5-desk3.ch.intel.com Link: http://lkml.kernel.org/r/148545058784.17912.6353162518188733642.stgit@djiang5-desk3.ch.intel.com Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com> Signed-off-by: Dave Jiang <dave.jiang@intel.com> Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Jan Kara <jack@suse.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Nilesh Choudhury <nilesh.choudhury@oracle.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Dave Jiang <dave.jiang@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/memory.c')
-rw-r--r--mm/memory.c18
1 files changed, 12 insertions, 6 deletions
diff --git a/mm/memory.c b/mm/memory.c
index cf97d88158cd..e721e8eba570 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3466,8 +3466,8 @@ static int create_huge_pmd(struct vm_fault *vmf)
{
if (vma_is_anonymous(vmf->vma))
return do_huge_pmd_anonymous_page(vmf);
- if (vmf->vma->vm_ops->pmd_fault)
- return vmf->vma->vm_ops->pmd_fault(vmf);
+ if (vmf->vma->vm_ops->huge_fault)
+ return vmf->vma->vm_ops->huge_fault(vmf);
return VM_FAULT_FALLBACK;
}
@@ -3475,8 +3475,8 @@ static int wp_huge_pmd(struct vm_fault *vmf, pmd_t orig_pmd)
{
if (vma_is_anonymous(vmf->vma))
return do_huge_pmd_wp_page(vmf, orig_pmd);
- if (vmf->vma->vm_ops->pmd_fault)
- return vmf->vma->vm_ops->pmd_fault(vmf);
+ if (vmf->vma->vm_ops->huge_fault)
+ return vmf->vma->vm_ops->huge_fault(vmf);
/* COW handled on pte level: split pmd */
VM_BUG_ON_VMA(vmf->vma->vm_flags & VM_SHARED, vmf->vma);
@@ -3606,6 +3606,7 @@ static int __handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
struct mm_struct *mm = vma->vm_mm;
pgd_t *pgd;
pud_t *pud;
+ int ret;
pgd = pgd_offset(mm, address);
pud = pud_alloc(mm, pgd, address);
@@ -3615,15 +3616,18 @@ static int __handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
if (!vmf.pmd)
return VM_FAULT_OOM;
if (pmd_none(*vmf.pmd) && transparent_hugepage_enabled(vma)) {
- int ret = create_huge_pmd(&vmf);
+ vmf.flags |= FAULT_FLAG_SIZE_PMD;
+ ret = create_huge_pmd(&vmf);
if (!(ret & VM_FAULT_FALLBACK))
return ret;
+ /* fall through path, remove PMD flag */
+ vmf.flags &= ~FAULT_FLAG_SIZE_PMD;
} else {
pmd_t orig_pmd = *vmf.pmd;
- int ret;
barrier();
if (pmd_trans_huge(orig_pmd) || pmd_devmap(orig_pmd)) {
+ vmf.flags |= FAULT_FLAG_SIZE_PMD;
if (pmd_protnone(orig_pmd) && vma_is_accessible(vma))
return do_huge_pmd_numa_page(&vmf, orig_pmd);
@@ -3632,6 +3636,8 @@ static int __handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
ret = wp_huge_pmd(&vmf, orig_pmd);
if (!(ret & VM_FAULT_FALLBACK))
return ret;
+ /* fall through path, remove PUD flag */
+ vmf.flags &= ~FAULT_FLAG_SIZE_PUD;
} else {
huge_pmd_set_accessed(&vmf, orig_pmd);
return 0;