parisc: Use per-pagetable spinlock

PA-RISC uses a global spinlock to protect pagetable updates in the TLB
fault handlers. When multiple cores are taking TLB faults simultaneously,
the cache line containing the spinlock becomes a bottleneck.

This patch embeds the spinlock in the top level page directory, so that
every process has its own lock. It improves performance by 30% when
doing parallel compilations.

At least on the N class systems, only one PxTLB inter processor
broadcast can be active at any one time on the Merced bus. If a Merced
bus is found, this patch serializes the TLB flushes with the
pa_tlb_flush_lock spinlock.

v1: Initial patch by Mikulas
v2: Added Merced detection by Helge
v3: Revised TLB serialization by Dave & Helge

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: John David Anglin <dave.anglin@bell.net>
Signed-off-by: Helge Deller <deller@gmx.de>

1 files changed, 54 insertions, 15 deletions

diff --git a/arch/parisc/include/asm/pgtable.h b/arch/parisc/include/asm/pgtable.h
index c7bb74e22436..a39b079e73f2 100644
--- a/arch/parisc/include/asm/pgtable.h
+++ b/arch/parisc/include/asm/pgtable.h
@@ -17,7 +17,7 @@
 #include <asm/processor.h>
 #include <asm/cache.h>
 
-extern spinlock_t pa_tlb_lock;
+static inline spinlock_t *pgd_spinlock(pgd_t *);
 
 /*
  * kern_addr_valid(ADDR) tests if ADDR is pointing to valid kernel
@@ -34,16 +34,46 @@ extern spinlock_t pa_tlb_lock;
  */
 #define kern_addr_valid(addr)	(1)
 
-/* Purge data and instruction TLB entries.  Must be called holding
- * the pa_tlb_lock.  The TLB purge instructions are slow on SMP
- * machines since the purge must be broadcast to all CPUs.
+/* This is for the serialization of PxTLB broadcasts. At least on the N class
+ * systems, only one PxTLB inter processor broadcast can be active at any one
+ * time on the Merced bus.
+
+ * PTE updates are protected by locks in the PMD.
+ */
+extern spinlock_t pa_tlb_flush_lock;
+extern spinlock_t pa_swapper_pg_lock;
+#if defined(CONFIG_64BIT) && defined(CONFIG_SMP)
+extern int pa_serialize_tlb_flushes;
+#else
+#define pa_serialize_tlb_flushes        (0)
+#endif
+
+#define purge_tlb_start(flags)  do { \
+	if (pa_serialize_tlb_flushes)	\
+		spin_lock_irqsave(&pa_tlb_flush_lock, flags); \
+	else \
+		local_irq_save(flags);	\
+	} while (0)
+#define purge_tlb_end(flags)	do { \
+	if (pa_serialize_tlb_flushes)	\
+		spin_unlock_irqrestore(&pa_tlb_flush_lock, flags); \
+	else \
+		local_irq_restore(flags); \
+	} while (0)
+
+/* Purge data and instruction TLB entries. The TLB purge instructions
+ * are slow on SMP machines since the purge must be broadcast to all CPUs.
  */
 
 static inline void purge_tlb_entries(struct mm_struct *mm, unsigned long addr)
 {
+	unsigned long flags;
+
+	purge_tlb_start(flags);
 	mtsp(mm->context, 1);
 	pdtlb(addr);
 	pitlb(addr);
+	purge_tlb_end(flags);
 }
 
 /* Certain architectures need to do special things when PTEs
@@ -59,11 +89,11 @@ static inline void purge_tlb_entries(struct mm_struct *mm, unsigned long addr)
 	do {							\
 		pte_t old_pte;					\
 		unsigned long flags;				\
-		spin_lock_irqsave(&pa_tlb_lock, flags);		\
+		spin_lock_irqsave(pgd_spinlock((mm)->pgd), flags);\
 		old_pte = *ptep;				\
 		set_pte(ptep, pteval);				\
 		purge_tlb_entries(mm, addr);			\
-		spin_unlock_irqrestore(&pa_tlb_lock, flags);	\
+		spin_unlock_irqrestore(pgd_spinlock((mm)->pgd), flags);\
 	} while (0)
 
 #endif /* !__ASSEMBLY__ */
@@ -88,10 +118,10 @@ static inline void purge_tlb_entries(struct mm_struct *mm, unsigned long addr)
 #if CONFIG_PGTABLE_LEVELS == 3
 #define PGD_ORDER	1 /* Number of pages per pgd */
 #define PMD_ORDER	1 /* Number of pages per pmd */
-#define PGD_ALLOC_ORDER	2 /* first pgd contains pmd */
+#define PGD_ALLOC_ORDER	(2 + 1) /* first pgd contains pmd */
 #else
 #define PGD_ORDER	1 /* Number of pages per pgd */
-#define PGD_ALLOC_ORDER	PGD_ORDER
+#define PGD_ALLOC_ORDER	(PGD_ORDER + 1)
 #endif
 
 /* Definitions for 3rd level (we use PLD here for Page Lower directory
@@ -459,6 +489,15 @@ extern void update_mmu_cache(struct vm_area_struct *, unsigned long, pte_t *);
 #define __pte_to_swp_entry(pte)		((swp_entry_t) { pte_val(pte) })
 #define __swp_entry_to_pte(x)		((pte_t) { (x).val })
 
+
+static inline spinlock_t *pgd_spinlock(pgd_t *pgd)
+{
+	if (unlikely(pgd == swapper_pg_dir))
+		return &pa_swapper_pg_lock;
+	return (spinlock_t *)((char *)pgd + (PAGE_SIZE << (PGD_ALLOC_ORDER - 1)));
+}
+
+
 static inline int ptep_test_and_clear_young(struct vm_area_struct *vma, unsigned long addr, pte_t *ptep)
 {
 	pte_t pte;
@@ -467,15 +506,15 @@ static inline int ptep_test_and_clear_young(struct vm_area_struct *vma, unsigned
 	if (!pte_young(*ptep))
 		return 0;
 
-	spin_lock_irqsave(&pa_tlb_lock, flags);
+	spin_lock_irqsave(pgd_spinlock(vma->vm_mm->pgd), flags);
 	pte = *ptep;
 	if (!pte_young(pte)) {
-		spin_unlock_irqrestore(&pa_tlb_lock, flags);
+		spin_unlock_irqrestore(pgd_spinlock(vma->vm_mm->pgd), flags);
 		return 0;
 	}
 	set_pte(ptep, pte_mkold(pte));
 	purge_tlb_entries(vma->vm_mm, addr);
-	spin_unlock_irqrestore(&pa_tlb_lock, flags);
+	spin_unlock_irqrestore(pgd_spinlock(vma->vm_mm->pgd), flags);
 	return 1;
 }
 
@@ -485,11 +524,11 @@ static inline pte_t ptep_get_and_clear(struct mm_struct *mm, unsigned long addr,
 	pte_t old_pte;
 	unsigned long flags;
 
-	spin_lock_irqsave(&pa_tlb_lock, flags);
+	spin_lock_irqsave(pgd_spinlock(mm->pgd), flags);
 	old_pte = *ptep;
 	set_pte(ptep, __pte(0));
 	purge_tlb_entries(mm, addr);
-	spin_unlock_irqrestore(&pa_tlb_lock, flags);
+	spin_unlock_irqrestore(pgd_spinlock(mm->pgd), flags);
 
 	return old_pte;
 }
@@ -497,10 +536,10 @@ static inline pte_t ptep_get_and_clear(struct mm_struct *mm, unsigned long addr,
 static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long addr, pte_t *ptep)
 {
 	unsigned long flags;
-	spin_lock_irqsave(&pa_tlb_lock, flags);
+	spin_lock_irqsave(pgd_spinlock(mm->pgd), flags);
 	set_pte(ptep, pte_wrprotect(*ptep));
 	purge_tlb_entries(mm, addr);
-	spin_unlock_irqrestore(&pa_tlb_lock, flags);
+	spin_unlock_irqrestore(pgd_spinlock(mm->pgd), flags);
 }
 
 #define pte_same(A,B)	(pte_val(A) == pte_val(B))