mm: numa: slow PTE scan rate if migration failures occur

[cascardo/linux.git] / mm / huge_memory.c

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 626e93d..51b3e7c 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1260,6 +1260,7 @@ int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
        int target_nid, last_cpupid = -1;
        bool page_locked;
        bool migrated = false;
+       bool was_writable;
        int flags = 0;
 
        /* A PROT_NONE fault should not end up here */
@@ -1291,17 +1292,8 @@ int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
                flags |= TNF_FAULT_LOCAL;
        }
 
-       /*
-        * Avoid grouping on DSO/COW pages in specific and RO pages
-        * in general, RO pages shouldn't hurt as much anyway since
-        * they can be in shared cache state.
-        *
-        * FIXME! This checks "pmd_dirty()" as an approximation of
-        * "is this a read-only page", since checking "pmd_write()"
-        * is even more broken. We haven't actually turned this into
-        * a writable page, so pmd_write() will always be false.
-        */
-       if (!pmd_dirty(pmd))
+       /* See similar comment in do_numa_page for explanation */
+       if (!(vma->vm_flags & VM_WRITE))
                flags |= TNF_NO_GROUP;
 
        /*
@@ -1358,12 +1350,16 @@ int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
        if (migrated) {
                flags |= TNF_MIGRATED;
                page_nid = target_nid;
-       }
+       } else
+               flags |= TNF_MIGRATE_FAIL;
 
        goto out;
 clear_pmdnuma:
        BUG_ON(!PageLocked(page));
+       was_writable = pmd_write(pmd);
        pmd = pmd_modify(pmd, vma->vm_page_prot);
+       if (was_writable)
+               pmd = pmd_mkwrite(pmd);
        set_pmd_at(mm, haddr, pmdp, pmd);
        update_mmu_cache_pmd(vma, addr, pmdp);
        unlock_page(page);
@@ -1487,6 +1483,7 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
 
        if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
                pmd_t entry;
+               bool preserve_write = prot_numa && pmd_write(*pmd);
                ret = 1;
 
                /*
@@ -1502,9 +1499,11 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
                if (!prot_numa || !pmd_protnone(*pmd)) {
                        entry = pmdp_get_and_clear_notify(mm, addr, pmd);
                        entry = pmd_modify(entry, newprot);
+                       if (preserve_write)
+                               entry = pmd_mkwrite(entry);
                        ret = HPAGE_PMD_NR;
                        set_pmd_at(mm, addr, pmd, entry);
-                       BUG_ON(pmd_write(entry));
+                       BUG_ON(!preserve_write && pmd_write(entry));
                }
                spin_unlock(ptl);
        }