1 files changed, 87 insertions, 8 deletions

diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index 6fb6927f9e76..5a7e5252c878 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -190,7 +190,7 @@ void pud_populate(struct mm_struct *mm, pud_t *pudp, pmd_t *pmd)
 
 #endif	/* CONFIG_X86_PAE */
 
-static void free_pmds(pmd_t *pmds[])
+static void free_pmds(struct mm_struct *mm, pmd_t *pmds[])
 {
 	int i;
 
@@ -198,10 +198,11 @@ static void free_pmds(pmd_t *pmds[])
 		if (pmds[i]) {
 			pgtable_pmd_page_dtor(virt_to_page(pmds[i]));
 			free_page((unsigned long)pmds[i]);
+			mm_dec_nr_pmds(mm);
 		}
 }
 
-static int preallocate_pmds(pmd_t *pmds[])
+static int preallocate_pmds(struct mm_struct *mm, pmd_t *pmds[])
 {
 	int i;
 	bool failed = false;
@@ -215,11 +216,13 @@ static int preallocate_pmds(pmd_t *pmds[])
 			pmd = NULL;
 			failed = true;
 		}
+		if (pmd)
+			mm_inc_nr_pmds(mm);
 		pmds[i] = pmd;
 	}
 
 	if (failed) {
-		free_pmds(pmds);
+		free_pmds(mm, pmds);
 		return -ENOMEM;
 	}
 
@@ -246,6 +249,7 @@ static void pgd_mop_up_pmds(struct mm_struct *mm, pgd_t *pgdp)
 
 			paravirt_release_pmd(pgd_val(pgd) >> PAGE_SHIFT);
 			pmd_free(mm, pmd);
+			mm_dec_nr_pmds(mm);
 		}
 	}
 }
@@ -271,19 +275,94 @@ static void pgd_prepopulate_pmd(struct mm_struct *mm, pgd_t *pgd, pmd_t *pmds[])
 	}
 }
 
+/*
+ * Xen paravirt assumes pgd table should be in one page. 64 bit kernel also
+ * assumes that pgd should be in one page.
+ *
+ * But kernel with PAE paging that is not running as a Xen domain
+ * only needs to allocate 32 bytes for pgd instead of one page.
+ */
+#ifdef CONFIG_X86_PAE
+
+#include <linux/slab.h>
+
+#define PGD_SIZE	(PTRS_PER_PGD * sizeof(pgd_t))
+#define PGD_ALIGN	32
+
+static struct kmem_cache *pgd_cache;
+
+static int __init pgd_cache_init(void)
+{
+	/*
+	 * When PAE kernel is running as a Xen domain, it does not use
+	 * shared kernel pmd. And this requires a whole page for pgd.
+	 */
+	if (!SHARED_KERNEL_PMD)
+		return 0;
+
+	/*
+	 * when PAE kernel is not running as a Xen domain, it uses
+	 * shared kernel pmd. Shared kernel pmd does not require a whole
+	 * page for pgd. We are able to just allocate a 32-byte for pgd.
+	 * During boot time, we create a 32-byte slab for pgd table allocation.
+	 */
+	pgd_cache = kmem_cache_create("pgd_cache", PGD_SIZE, PGD_ALIGN,
+				      SLAB_PANIC, NULL);
+	if (!pgd_cache)
+		return -ENOMEM;
+
+	return 0;
+}
+core_initcall(pgd_cache_init);
+
+static inline pgd_t *_pgd_alloc(void)
+{
+	/*
+	 * If no SHARED_KERNEL_PMD, PAE kernel is running as a Xen domain.
+	 * We allocate one page for pgd.
+	 */
+	if (!SHARED_KERNEL_PMD)
+		return (pgd_t *)__get_free_page(PGALLOC_GFP);
+
+	/*
+	 * Now PAE kernel is not running as a Xen domain. We can allocate
+	 * a 32-byte slab for pgd to save memory space.
+	 */
+	return kmem_cache_alloc(pgd_cache, PGALLOC_GFP);
+}
+
+static inline void _pgd_free(pgd_t *pgd)
+{
+	if (!SHARED_KERNEL_PMD)
+		free_page((unsigned long)pgd);
+	else
+		kmem_cache_free(pgd_cache, pgd);
+}
+#else
+static inline pgd_t *_pgd_alloc(void)
+{
+	return (pgd_t *)__get_free_page(PGALLOC_GFP);
+}
+
+static inline void _pgd_free(pgd_t *pgd)
+{
+	free_page((unsigned long)pgd);
+}
+#endif /* CONFIG_X86_PAE */
+
 pgd_t *pgd_alloc(struct mm_struct *mm)
 {
 	pgd_t *pgd;
 	pmd_t *pmds[PREALLOCATED_PMDS];
 
-	pgd = (pgd_t *)__get_free_page(PGALLOC_GFP);
+	pgd = _pgd_alloc();
 
 	if (pgd == NULL)
 		goto out;
 
 	mm->pgd = pgd;
 
-	if (preallocate_pmds(pmds) != 0)
+	if (preallocate_pmds(mm, pmds) != 0)
 		goto out_free_pgd;
 
 	if (paravirt_pgd_alloc(mm) != 0)
@@ -304,9 +383,9 @@ pgd_t *pgd_alloc(struct mm_struct *mm)
 	return pgd;
 
 out_free_pmds:
-	free_pmds(pmds);
+	free_pmds(mm, pmds);
 out_free_pgd:
-	free_page((unsigned long)pgd);
+	_pgd_free(pgd);
 out:
 	return NULL;
 }
@@ -316,7 +395,7 @@ void pgd_free(struct mm_struct *mm, pgd_t *pgd)
 	pgd_mop_up_pmds(mm, pgd);
 	pgd_dtor(pgd);
 	paravirt_pgd_free(mm, pgd);
-	free_page((unsigned long)pgd);
+	_pgd_free(pgd);
 }
 
 /*