WebSVN – HelenOS-historic – Diff – /kernel/trunk/generic/src/mm/slab.c

  * from non-cpu-cached mag. cache). This would provide a nice per-cpu
  * buffer. The other possibility is to use the per-cache
  * 'empty-magazine-list', which decreases competing for 1 per-system
  * magazine cache.
+ *
+ * - it might be good to add granularity of locks even to slab level,
+ *   we could then try_spinlock over all partial slabs and thus improve
+ *   scalability even on slab level
  */
 #include <synch/spinlock.h>
 #include <mm/slab.h>
 /**
  * Return object to slab and call a destructor
+ *
- * Assume the cache->lock is held;
- *
  * @param slab If the caller knows directly slab of the object, otherwise NULL
+ *
  * @return Number of freed pages
  */
 static count_t slab_obj_destroy(slab_cache_t *cache, void *obj,
     if (!slab)
         slab = obj2slab(obj);
     ASSERT(slab->cache == cache);
+    spinlock_lock(&cache->slablock);
     *((int *)obj) = slab->nextavail;
     slab->nextavail = (obj - slab->start)/cache->size;
     slab->available++;
     /* Move it to correct list */
         list_prepend(&slab->link, &cache->partial_slabs);
+    }
     if (slab->available == cache->objects) {
         /* Free associated memory */
         list_remove(&slab->link);
-        /* Avoid deadlock */
+        /* This should not produce deadlock, as
+         * magazine is always allocated with NO reclaim,
-        spinlock_unlock(&cache->lock);
+         * keep all locks */
         frames = slab_space_free(cache, slab);
-        spinlock_lock(&cache->lock);
+    }
+    spinlock_unlock(&cache->slablock);
     return frames;
+}
 /**
  * Take new object from slab or create new if needed
+ *
- * Assume cache->lock is held.
- *
  * @return Object address or null
  */
 static void * slab_obj_create(slab_cache_t *cache, int flags)
+{
     slab_t *slab;
     void *obj;
+    spinlock_lock(&cache->slablock);
     if (list_empty(&cache->partial_slabs)) {
         /* Allow recursion and reclaiming
          * - this should work, as the SLAB control structures
          *   are small and do not need to allocte with anything
          *   other ten frame_alloc when they are allocating,
          *   that's why we should get recursion at most 1-level deep
          */
-        spinlock_unlock(&cache->lock);
+        spinlock_unlock(&cache->slablock);
         slab = slab_space_alloc(cache, flags);
-        spinlock_lock(&cache->lock);
+        spinlock_lock(&cache->slablock);
-        if (!slab) {
+        if (!slab)
-            return NULL;
+            goto err;
-        }
     } else {
         slab = list_get_instance(cache->partial_slabs.next,
                      slab_t,
                      link);
         list_remove(&slab->link);
     slab->available--;
     if (! slab->available)
         list_prepend(&slab->link, &cache->full_slabs);
     else
         list_prepend(&slab->link, &cache->partial_slabs);
+    spinlock_unlock(&cache->slablock);
     return obj;
+err:
+    spinlock_unlock(&cache->slablock);
+    return NULL;
+}
 /**************************************/
 /* CPU-Cache slab functions */
 /**
  * Free all objects in magazine and free memory associated with magazine
+ *
- * Assume cache->lock is held
- *
  * @return Number of freed pages
  */
 static count_t magazine_destroy(slab_cache_t *cache,
                 slab_magazine_t *mag)
+{
             cache->mag_cache[CPU->id].last = cmag;
             return lastmag;
+        }
+    }
     /* Local magazines are empty, import one from magazine list */
-    spinlock_lock(&cache->lock);
+    spinlock_lock(&cache->maglock);
     if (list_empty(&cache->magazines)) {
-        spinlock_unlock(&cache->lock);
+        spinlock_unlock(&cache->maglock);
         return NULL;
+    }
     newmag = list_get_instance(cache->magazines.next,
                    slab_magazine_t,
                    link);
     list_remove(&newmag->link);
-    spinlock_unlock(&cache->lock);
+    spinlock_unlock(&cache->maglock);
     if (lastmag)
         slab_free(&mag_cache, lastmag);
     cache->mag_cache[CPU->id].last = cmag;
     cache->mag_cache[CPU->id].current = newmag;
     newmag->size = SLAB_MAG_SIZE;
     newmag->busy = 0;
     /* Flush last to magazine list */
     if (lastmag) {
-        spinlock_lock(&cache->lock);
+        spinlock_lock(&cache->maglock);
         list_prepend(&lastmag->link, &cache->magazines);
-        spinlock_unlock(&cache->lock);
+        spinlock_unlock(&cache->maglock);
+    }
     /* Move current as last, save new as current */
     cache->mag_cache[CPU->id].last = cmag;
     cache->mag_cache[CPU->id].current = newmag;
     cache->flags = flags;
     list_initialize(&cache->full_slabs);
     list_initialize(&cache->partial_slabs);
     list_initialize(&cache->magazines);
-    spinlock_initialize(&cache->lock, "cachelock");
+    spinlock_initialize(&cache->slablock, "slab_lock");
+    spinlock_initialize(&cache->maglock, "slab_maglock");
     if (! (cache->flags & SLAB_CACHE_NOMAGAZINE)) {
         for (i=0; i < config.cpu_count; i++) {
             memsetb((__address)&cache->mag_cache[i],
                 sizeof(cache->mag_cache[i]), 0);
             spinlock_initialize(&cache->mag_cache[i].lock,
-                        "cpucachelock");
+                        "slab_maglock_cpu");
+        }
+    }
     /* Compute slab sizes, object counts in slabs etc. */
     if (cache->size < SLAB_INSIDE_SIZE)
     /* First lock all cpu caches, then the complete cache lock */
     if (flags & SLAB_RECLAIM_ALL) {
         for (i=0; i < config.cpu_count; i++)
             spinlock_lock(&cache->mag_cache[i].lock);
+    }
-    spinlock_lock(&cache->lock);
+    spinlock_lock(&cache->maglock);
     if (flags & SLAB_RECLAIM_ALL) {
         /* Aggressive memfree */
         /* Destroy CPU magazines */
         for (i=0; i<config.cpu_count; i++) {
             if (mag)
                 frames += magazine_destroy(cache, mag);
             cache->mag_cache[i].last = NULL;
+        }
+    }
+    /* We can release the cache locks now */
+    if (flags & SLAB_RECLAIM_ALL) {
+        for (i=0; i < config.cpu_count; i++)
+            spinlock_unlock(&cache->mag_cache[i].lock);
+    }
     /* Destroy full magazines */
     cur=cache->magazines.prev;
     while (cur != &cache->magazines) {
         mag = list_get_instance(cur, slab_magazine_t, link);
          * as soon as something is freed */
         if (!(flags & SLAB_RECLAIM_ALL) && frames)
             break;
+    }
-    spinlock_unlock(&cache->lock);
+    spinlock_unlock(&cache->maglock);
-    /* We can release the cache locks now */
-    if (flags & SLAB_RECLAIM_ALL) {
-        for (i=0; i < config.cpu_count; i++)
-            spinlock_unlock(&cache->mag_cache[i].lock);
-    }
     return frames;
+}
 /** Check that there are no slabs and remove cache from system  */
     ipl = interrupts_disable();
     if (!(cache->flags & SLAB_CACHE_NOMAGAZINE))
         result = magazine_obj_get(cache);
-    if (!result) {
+    if (!result)
-        spinlock_lock(&cache->lock);
         result = slab_obj_create(cache, flags);
-        spinlock_unlock(&cache->lock);
-    }
     interrupts_restore(ipl);
     if (result)
         atomic_inc(&cache->allocated_objs);
     ipl = interrupts_disable();
     if ((cache->flags & SLAB_CACHE_NOMAGAZINE) \
         || magazine_obj_put(cache, obj)) {
-        spinlock_lock(&cache->lock);
         slab_obj_destroy(cache, obj, slab);
-        spinlock_unlock(&cache->lock);
+    }
     interrupts_restore(ipl);
     atomic_dec(&cache->allocated_objs);
+}
     link_t *cur;
     count_t frames = 0;
     spinlock_lock(&slab_cache_lock);
+    /* TODO: Add assert, that interrupts are disabled, otherwise
+     * memory allocation from interrupts can deadlock.
+     */
     for (cur = slab_cache_list.next;cur!=&slab_cache_list; cur=cur->next) {
         cache = list_get_instance(cur, slab_cache_t, link);
         frames += _slab_reclaim(cache, flags);
+    }

Subversion Repositories HelenOS-historic

(root)/kernel/trunk/generic/src/mm/slab.c – Rev 775 → 776