Changeset fb63c06 in mainline

Timestamp:

2016-09-01T16:37:51Z (8 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

2a2fbc8

Parents:

346b12a2

Message:

Make page hash table critical sections smaller

After the change of the page mapping interface to work exclusively with
a copy of the actual PTE, the critical section around page hash table
look-ups, insertions and deletions can be much smaller.

This change necessitated the change of the page_ht_lock mutex into a
spinlock, because the page mapping API can be used from within TLB
shootdown sequence, which is basically a spinlock-protected critical
section and we cannot take a mutex while holding a spinlock.

Location:

kernel/genarch

Files:

• include/genarch/mm/page_ht.h (modified) (2 diffs)
• src/mm/as_ht.c (modified) (5 diffs)
• src/mm/page_ht.c (modified) (9 diffs)

kernel/genarch/include/genarch/mm/page_ht.h

@@ -44 +44 @@
 #include <mm/page.h>
 #include <mm/slab.h>
-#include <synch/mutex.h>
 #include <adt/hash_table.h>
 
@@ -66 +65 @@
 
 extern slab_cache_t *pte_cache;
-extern mutex_t page_ht_lock;
 extern hash_table_t page_ht;
 extern hash_table_operations_t ht_operations;

kernel/genarch/src/mm/as_ht.c

@@ -77 +77 @@
         if (flags & FLAG_AS_KERNEL) {
                 hash_table_create(&page_ht, PAGE_HT_ENTRIES, 2, &ht_operations);
-                mutex_initialize(&page_ht_lock, MUTEX_PASSIVE);
                 pte_cache = slab_cache_create("pte_t", sizeof(pte_t), 0,
                     NULL, NULL, SLAB_CACHE_MAGDEFERRED);
@@ -99 +98 @@
 /** Lock page table.
  *
- * Lock address space and page hash table.
+ * Lock address space.
  * Interrupts must be disabled.
  *
@@ -110 +109 @@
         if (lock)
                 mutex_lock(&as->lock);
-        
-        mutex_lock(&page_ht_lock);
 }
 
 /** Unlock page table.
  *
- * Unlock address space and page hash table.
+ * Unlock address space.
  * Interrupts must be disabled.
  *
@@ -125 +122 @@
 void ht_unlock(as_t *as, bool unlock)
 {
-        mutex_unlock(&page_ht_lock);
-        
         if (unlock)
                 mutex_unlock(&as->lock);
@@ -140 +135 @@
 bool ht_locked(as_t *as)
 {
-        return (mutex_locked(&page_ht_lock) && mutex_locked(&as->lock));
+        return mutex_locked(&as->lock);
 }
 

kernel/genarch/src/mm/page_ht.c

@@ -71 +71 @@
  *
  */
-mutex_t page_ht_lock;
+IRQ_SPINLOCK_STATIC_INITIALIZE(page_ht_lock);
 
 /** Page hash table.
@@ -193 +193 @@
 
         ASSERT(page_table_locked(as));
+
+        irq_spinlock_lock(&page_ht_lock, true);
         
         if (!hash_table_find(&page_ht, key)) {
@@ -219 +221 @@
                 hash_table_insert(&page_ht, key, &pte->link);
         }
+
+        irq_spinlock_unlock(&page_ht_lock, true);
 }
 
@@ -240 +244 @@
         ASSERT(page_table_locked(as));
         
+        irq_spinlock_lock(&page_ht_lock, true);
+
         /*
          * Note that removed PTE's will be freed
@@ -245 +251 @@
          */
         hash_table_remove(&page_ht, key, 2);
+
+        irq_spinlock_unlock(&page_ht_lock, true);
 }
 
@@ -255 +263 @@
 
         ASSERT(nolock || page_table_locked(as));
-        
+
         link_t *cur = hash_table_find(&page_ht, key);
         if (cur)
@@ -274 +282 @@
 bool ht_mapping_find(as_t *as, uintptr_t page, bool nolock, pte_t *pte)
 {
+        irq_spinlock_lock(&page_ht_lock, true);
+
         pte_t *t = ht_mapping_find_internal(as, page, nolock);
         if (t)
                 *pte = *t;
+
+        irq_spinlock_unlock(&page_ht_lock, true);
         
         return t != NULL;
@@ -290 +302 @@
 void ht_mapping_update(as_t *as, uintptr_t page, bool nolock, pte_t *pte)
 {
+        irq_spinlock_lock(&page_ht_lock, true);
+
         pte_t *t = ht_mapping_find_internal(as, page, nolock);
         if (!t)
@@ -306 +320 @@
         t->a = pte->a;
         t->d = pte->d;
+
+        irq_spinlock_unlock(&page_ht_lock, true);
 }