[PATCH 4.4 56/75] sparc64: Reduce TLB flushes during hugepte changes

Greg Kroah-Hartman
2016-06-22T23:13:58Z

From: Nitin Gupta <nitin.m.gupta@oracle.com>

[ Upstream commit 24e49ee3d76b70853a96520e46b8837e5eae65b2 ]

During hugepage map/unmap, TSB and TLB flushes are currently
issued at every PAGE_SIZE'd boundary which is unnecessary.
We now issue the flush at REAL_HPAGE_SIZE boundaries only.

Without this patch workloads which unmap a large hugepage
backed VMA region get CPU lockups due to excessive TLB
flush calls.

Orabug: 22365539, 22643230, 22995196

Signed-off-by: Nitin Gupta <nitin.m.gupta@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/sparc/include/asm/pgtable_64.h | 43 ++++++++++++++++++++++++++---------
arch/sparc/include/asm/tlbflush_64.h | 3 +-
arch/sparc/mm/hugetlbpage.c | 33 ++++++++++++++++++++++----
arch/sparc/mm/init_64.c | 12 ---------
arch/sparc/mm/tlb.c | 25 ++++++++++++++------
arch/sparc/mm/tsb.c | 32 +++++++++++++-------------
6 files changed, 97 insertions(+), 51 deletions(-)

--- a/arch/sparc/include/asm/pgtable_64.h
+++ b/arch/sparc/include/asm/pgtable_64.h
@@ -375,7 +375,7 @@ static inline pgprot_t pgprot_noncached(
#define pgprot_noncached pgprot_noncached

#if defined(CONFIG_HUGETLB_PAGE) || defined(CONFIG_TRANSPARENT_HUGEPAGE)
-static inline pte_t pte_mkhuge(pte_t pte)
+static inline unsigned long __pte_huge_mask(void)
{
unsigned long mask;

@@ -390,8 +390,19 @@ static inline pte_t pte_mkhuge(pte_t pte
: "=r" (mask)
: "i" (_PAGE_SZHUGE_4U), "i" (_PAGE_SZHUGE_4V));

- return __pte(pte_val(pte) | mask);
+ return mask;
+}
+
+static inline pte_t pte_mkhuge(pte_t pte)
+{
+ return __pte(pte_val(pte) | __pte_huge_mask());
+}
+
+static inline bool is_hugetlb_pte(pte_t pte)
+{
+ return !!(pte_val(pte) & __pte_huge_mask());
}
+
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
static inline pmd_t pmd_mkhuge(pmd_t pmd)
{
@@ -403,6 +414,11 @@ static inline pmd_t pmd_mkhuge(pmd_t pmd
return __pmd(pte_val(pte));
}
#endif
+#else
+static inline bool is_hugetlb_pte(pte_t pte)
+{
+ return false;
+}
#endif

static inline pte_t pte_mkdirty(pte_t pte)
@@ -865,6 +881,19 @@ static inline unsigned long pud_pfn(pud_
void tlb_batch_add(struct mm_struct *mm, unsigned long vaddr,
pte_t *ptep, pte_t orig, int fullmm);

+static void maybe_tlb_batch_add(struct mm_struct *mm, unsigned long vaddr,
+ pte_t *ptep, pte_t orig, int fullmm)
+{
+ /* It is more efficient to let flush_tlb_kernel_range()
+ * handle init_mm tlb flushes.
+ *
+ * SUN4V NOTE: _PAGE_VALID is the same value in both the SUN4U
+ * and SUN4V pte layout, so this inline test is fine.
+ */
+ if (likely(mm != &init_mm) && pte_accessible(mm, orig))
+ tlb_batch_add(mm, vaddr, ptep, orig, fullmm);
+}
+
#define __HAVE_ARCH_PMDP_HUGE_GET_AND_CLEAR
static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm,
unsigned long addr,
@@ -881,15 +910,7 @@ static inline void __set_pte_at(struct m
pte_t orig = *ptep;

*ptep = pte;
-
- /* It is more efficient to let flush_tlb_kernel_range()
- * handle init_mm tlb flushes.
- *
- * SUN4V NOTE: _PAGE_VALID is the same value in both the SUN4U
- * and SUN4V pte layout, so this inline test is fine.
- */
- if (likely(mm != &init_mm) && pte_accessible(mm, orig))
- tlb_batch_add(mm, addr, ptep, orig, fullmm);
+ maybe_tlb_batch_add(mm, addr, ptep, orig, fullmm);
}

#define set_pte_at(mm,addr,ptep,pte) \
--- a/arch/sparc/include/asm/tlbflush_64.h
+++ b/arch/sparc/include/asm/tlbflush_64.h
@@ -8,6 +8,7 @@
#define TLB_BATCH_NR 192

struct tlb_batch {
+ bool huge;
struct mm_struct *mm;
unsigned long tlb_nr;
unsigned long active;
@@ -16,7 +17,7 @@ struct tlb_batch {

void flush_tsb_kernel_range(unsigned long start, unsigned long end);
void flush_tsb_user(struct tlb_batch *tb);
-void flush_tsb_user_page(struct mm_struct *mm, unsigned long vaddr);
+void flush_tsb_user_page(struct mm_struct *mm, unsigned long vaddr, bool huge);

/* TLB flush operations. */

--- a/arch/sparc/mm/hugetlbpage.c
+++ b/arch/sparc/mm/hugetlbpage.c
@@ -176,17 +176,31 @@ void set_huge_pte_at(struct mm_struct *m
pte_t *ptep, pte_t entry)
{
int i;
+ pte_t orig[2];
+ unsigned long nptes;

if (!pte_present(*ptep) && pte_present(entry))
mm->context.huge_pte_count++;

addr &= HPAGE_MASK;
- for (i = 0; i < (1 << HUGETLB_PAGE_ORDER); i++) {
- set_pte_at(mm, addr, ptep, entry);
+
+ nptes = 1 << HUGETLB_PAGE_ORDER;
+ orig[0] = *ptep;
+ orig[1] = *(ptep + nptes / 2);
+ for (i = 0; i < nptes; i++) {
+ *ptep = entry;
ptep++;
addr += PAGE_SIZE;
pte_val(entry) += PAGE_SIZE;
}
+
+ /* Issue TLB flush at REAL_HPAGE_SIZE boundaries */
+ addr -= REAL_HPAGE_SIZE;
+ ptep -= nptes / 2;
+ maybe_tlb_batch_add(mm, addr, ptep, orig[1], 0);
+ addr -= REAL_HPAGE_SIZE;
+ ptep -= nptes / 2;
+ maybe_tlb_batch_add(mm, addr, ptep, orig[0], 0);
}

pte_t huge_ptep_get_and_clear(struct mm_struct *mm, unsigned long addr,
@@ -194,19 +208,28 @@ pte_t huge_ptep_get_and_clear(struct mm_
{
pte_t entry;
int i;
+ unsigned long nptes;

entry = *ptep;
if (pte_present(entry))
mm->context.huge_pte_count--;

addr &= HPAGE_MASK;
-
- for (i = 0; i < (1 << HUGETLB_PAGE_ORDER); i++) {
- pte_clear(mm, addr, ptep);
+ nptes = 1 << HUGETLB_PAGE_ORDER;
+ for (i = 0; i < nptes; i++) {
+ *ptep = __pte(0UL);
addr += PAGE_SIZE;
ptep++;
}

+ /* Issue TLB flush at REAL_HPAGE_SIZE boundaries */
+ addr -= REAL_HPAGE_SIZE;
+ ptep -= nptes / 2;
+ maybe_tlb_batch_add(mm, addr, ptep, entry, 0);
+ addr -= REAL_HPAGE_SIZE;
+ ptep -= nptes / 2;
+ maybe_tlb_batch_add(mm, addr, ptep, entry, 0);
+
return entry;
}

--- a/arch/sparc/mm/init_64.c
+++ b/arch/sparc/mm/init_64.c
@@ -324,18 +324,6 @@ static void __update_mmu_tsb_insert(stru
tsb_insert(tsb, tag, tte);
}

-#if defined(CONFIG_HUGETLB_PAGE) || defined(CONFIG_TRANSPARENT_HUGEPAGE)
-static inline bool is_hugetlb_pte(pte_t pte)
-{
- if ((tlb_type == hypervisor &&
- (pte_val(pte) & _PAGE_SZALL_4V) == _PAGE_SZHUGE_4V) ||
- (tlb_type != hypervisor &&
- (pte_val(pte) & _PAGE_SZALL_4U) == _PAGE_SZHUGE_4U))
- return true;
- return false;
-}
-#endif
-
void update_mmu_cache(struct vm_area_struct *vma, unsigned long address, pte_t *ptep)
{
struct mm_struct *mm;
--- a/arch/sparc/mm/tlb.c
+++ b/arch/sparc/mm/tlb.c
@@ -67,7 +67,7 @@ void arch_leave_lazy_mmu_mode(void)
}

static void tlb_batch_add_one(struct mm_struct *mm, unsigned long vaddr,
- bool exec)
+ bool exec, bool huge)
{
struct tlb_batch *tb = &get_cpu_var(tlb_batch);
unsigned long nr;
@@ -84,13 +84,21 @@ static void tlb_batch_add_one(struct mm_
}

if (!tb->active) {
- flush_tsb_user_page(mm, vaddr);
+ flush_tsb_user_page(mm, vaddr, huge);
global_flush_tlb_page(mm, vaddr);
goto out;
}

- if (nr == 0)
+ if (nr == 0) {
tb->mm = mm;
+ tb->huge = huge;
+ }
+
+ if (tb->huge != huge) {
+ flush_tlb_pending();
+ tb->huge = huge;
+ nr = 0;
+ }

tb->vaddrs[nr] = vaddr;
tb->tlb_nr = ++nr;
@@ -104,6 +112,8 @@ out:
void tlb_batch_add(struct mm_struct *mm, unsigned long vaddr,
pte_t *ptep, pte_t orig, int fullmm)
{
+ bool huge = is_hugetlb_pte(orig);
+
if (tlb_type != hypervisor &&
pte_dirty(orig)) {
unsigned long paddr, pfn = pte_pfn(orig);
@@ -129,7 +139,7 @@ void tlb_batch_add(struct mm_struct *mm,

no_cache_flush:
if (!fullmm)
- tlb_batch_add_one(mm, vaddr, pte_exec(orig));
+ tlb_batch_add_one(mm, vaddr, pte_exec(orig), huge);
}

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
@@ -145,7 +155,7 @@ static void tlb_batch_pmd_scan(struct mm
if (pte_val(*pte) & _PAGE_VALID) {
bool exec = pte_exec(*pte);

- tlb_batch_add_one(mm, vaddr, exec);
+ tlb_batch_add_one(mm, vaddr, exec, false);
}
pte++;
vaddr += PAGE_SIZE;
@@ -185,8 +195,9 @@ void set_pmd_at(struct mm_struct *mm, un
pte_t orig_pte = __pte(pmd_val(orig));
bool exec = pte_exec(orig_pte);

- tlb_batch_add_one(mm, addr, exec);
- tlb_batch_add_one(mm, addr + REAL_HPAGE_SIZE, exec);
+ tlb_batch_add_one(mm, addr, exec, true);
+ tlb_batch_add_one(mm, addr + REAL_HPAGE_SIZE, exec,
+ true);
} else {
tlb_batch_pmd_scan(mm, addr, orig);
}
--- a/arch/sparc/mm/tsb.c
+++ b/arch/sparc/mm/tsb.c
@@ -76,14 +76,15 @@ void flush_tsb_user(struct tlb_batch *tb

spin_lock_irqsave(&mm->context.lock, flags);

- base = (unsigned long) mm->context.tsb_block[MM_TSB_BASE].tsb;
- nentries = mm->context.tsb_block[MM_TSB_BASE].tsb_nentries;
- if (tlb_type == cheetah_plus || tlb_type == hypervisor)
- base = __pa(base);
- __flush_tsb_one(tb, PAGE_SHIFT, base, nentries);
-
+ if (!tb->huge) {
+ base = (unsigned long) mm->context.tsb_block[MM_TSB_BASE].tsb;
+ nentries = mm->context.tsb_block[MM_TSB_BASE].tsb_nentries;
+ if (tlb_type == cheetah_plus || tlb_type == hypervisor)
+ base = __pa(base);
+ __flush_tsb_one(tb, PAGE_SHIFT, base, nentries);
+ }
#if defined(CONFIG_HUGETLB_PAGE) || defined(CONFIG_TRANSPARENT_HUGEPAGE)
- if (mm->context.tsb_block[MM_TSB_HUGE].tsb) {
+ if (tb->huge && mm->context.tsb_block[MM_TSB_HUGE].tsb) {
base = (unsigned long) mm->context.tsb_block[MM_TSB_HUGE].tsb;
nentries = mm->context.tsb_block[MM_TSB_HUGE].tsb_nentries;
if (tlb_type == cheetah_plus || tlb_type == hypervisor)
@@ -94,20 +95,21 @@ void flush_tsb_user(struct tlb_batch *tb
spin_unlock_irqrestore(&mm->context.lock, flags);
}

-void flush_tsb_user_page(struct mm_struct *mm, unsigned long vaddr)
+void flush_tsb_user_page(struct mm_struct *mm, unsigned long vaddr, bool huge)
{
unsigned long nentries, base, flags;

spin_lock_irqsave(&mm->context.lock, flags);

- base = (unsigned long) mm->context.tsb_block[MM_TSB_BASE].tsb;
- nentries = mm->context.tsb_block[MM_TSB_BASE].tsb_nentries;
- if (tlb_type == cheetah_plus || tlb_type == hypervisor)
- base = __pa(base);
- __flush_tsb_one_entry(base, vaddr, PAGE_SHIFT, nentries);
-
+ if (!huge) {
+ base = (unsigned long) mm->context.tsb_block[MM_TSB_BASE].tsb;
+ nentries = mm->context.tsb_block[MM_TSB_BASE].tsb_nentries;
+ if (tlb_type == cheetah_plus || tlb_type == hypervisor)
+ base = __pa(base);
+ __flush_tsb_one_entry(base, vaddr, PAGE_SHIFT, nentries);
+ }
#if defined(CONFIG_HUGETLB_PAGE) || defined(CONFIG_TRANSPARENT_HUGEPAGE)
- if (mm->context.tsb_block[MM_TSB_HUGE].tsb) {
+ if (huge && mm->context.tsb_block[MM_TSB_HUGE].tsb) {
base = (unsigned long) mm->context.tsb_block[MM_TSB_HUGE].tsb;
nentries = mm->context.tsb_block[MM_TSB_HUGE].tsb_nentries;
if (tlb_type == cheetah_plus || tlb_type == hypervisor)