c/mirror_zfs
1
0
Fork 0
mirror of https://git.proxmox.com/git/mirror_zfs.git synced 2026-05-22 02:27:36 +03:00
Code Issues Packages Projects Releases Wiki Activity

Track emergency object in rbtree

Browse Source 
In the initial implementation emergency objects were tracked on a
per-cache list.  The assumption was that under normal operation we
would never allocate more than a handful of these objects.  So the
cost of walking the list during free was expected to be negligible.

However real world usage has shown that emergency objects tend to
be allocated in batches.  A deadlock will be detected and several
thousand emergency objects will be allocated before the original
blocked slab allocation can complete.

Therefore the original list has been replaced by a red black tree
which is sorted by the memory address of each allocated object.
This bounds the worst case insertion and removal time to O(log n)
which minimize contention on the assoicated spin lock.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
This commit is contained in:
Brian Behlendorf
2012-10-30 10:45:50 -07:00
parent 165f13c33a
commit ed3163484d
2 changed files with 75 additions and 28 deletions
Download Patch File Download Diff File Expand all files Collapse all files
module/spl/spl-kmem.c
+72 -26
View File
@@ -1116,8 +1116,54 @@ spl_slab_reclaim(spl_kmem_cache_t *skc, int count, int flag)
SEXIT;
}
static spl_kmem_emergency_t *
spl_emergency_search(struct rb_root *root, void *obj)
{
struct rb_node *node = root->rb_node;
spl_kmem_emergency_t *ske;
unsigned long address = (unsigned long)obj;
while (node) {
ske = container_of(node, spl_kmem_emergency_t, ske_node);
if (address < (unsigned long)ske->ske_obj)
node = node->rb_left;
else if (address > (unsigned long)ske->ske_obj)
node = node->rb_right;
else
return ske;
}
return NULL;
}
static int
spl_emergency_insert(struct rb_root *root, spl_kmem_emergency_t *ske)
{
struct rb_node **new = &(root->rb_node), *parent = NULL;
spl_kmem_emergency_t *ske_tmp;
unsigned long address = (unsigned long)ske->ske_obj;
while (*new) {
ske_tmp = container_of(*new, spl_kmem_emergency_t, ske_node);
parent = *new;
if (address < (unsigned long)ske_tmp->ske_obj)
new = &((*new)->rb_left);
else if (address > (unsigned long)ske_tmp->ske_obj)
new = &((*new)->rb_right);
else
return 0;
}
rb_link_node(&ske->ske_node, parent, new);
rb_insert_color(&ske->ske_node, root);
return 1;
}
/*
* Allocate a single emergency object for use by the caller.
* Allocate a single emergency object and track it in a red black tree.
*/
static int
spl_emergency_alloc(spl_kmem_cache_t *skc, int flags, void **obj)
@@ -1143,48 +1189,49 @@ spl_emergency_alloc(spl_kmem_cache_t *skc, int flags, void **obj)
SRETURN(-ENOMEM);
}
spin_lock(&skc->skc_lock);
empty = spl_emergency_insert(&skc->skc_emergency_tree, ske);
if (likely(empty)) {
skc->skc_obj_total++;
skc->skc_obj_emergency++;
if (skc->skc_obj_emergency > skc->skc_obj_emergency_max)
skc->skc_obj_emergency_max = skc->skc_obj_emergency;
}
spin_unlock(&skc->skc_lock);
if (unlikely(!empty)) {
kfree(ske->ske_obj);
kfree(ske);
SRETURN(-EINVAL);
}
if (skc->skc_ctor)
skc->skc_ctor(ske->ske_obj, skc->skc_private, flags);
spin_lock(&skc->skc_lock);
skc->skc_obj_total++;
skc->skc_obj_emergency++;
if (skc->skc_obj_emergency > skc->skc_obj_emergency_max)
skc->skc_obj_emergency_max = skc->skc_obj_emergency;
list_add(&ske->ske_list, &skc->skc_emergency_list);
spin_unlock(&skc->skc_lock);
*obj = ske->ske_obj;
SRETURN(0);
}
/*
* Free the passed object if it is an emergency object or a normal slab
* object. Currently this is done by walking what should be a short list of
* emergency objects. If this proves to be too inefficient we can replace
* the simple list with a hash.
* Locate the passed object in the red black tree and free it.
*/
static int
spl_emergency_free(spl_kmem_cache_t *skc, void *obj)
{
spl_kmem_emergency_t *m, *n, *ske = NULL;
spl_kmem_emergency_t *ske;
SENTRY;
spin_lock(&skc->skc_lock);
list_for_each_entry_safe(m, n, &skc->skc_emergency_list, ske_list) {
if (m->ske_obj == obj) {
list_del(&m->ske_list);
skc->skc_obj_emergency--;
skc->skc_obj_total--;
ske = m;
break;
}
ske = spl_emergency_search(&skc->skc_emergency_tree, obj);
if (likely(ske)) {
rb_erase(&ske->ske_node, &skc->skc_emergency_tree);
skc->skc_obj_emergency--;
skc->skc_obj_total--;
}
spin_unlock(&skc->skc_lock);
if (ske == NULL)
if (unlikely(ske == NULL))
SRETURN(-ENOENT);
if (skc->skc_dtor)
@@ -1483,7 +1530,7 @@ spl_kmem_cache_create(char *name, size_t size, size_t align,
INIT_LIST_HEAD(&skc->skc_list);
INIT_LIST_HEAD(&skc->skc_complete_list);
INIT_LIST_HEAD(&skc->skc_partial_list);
INIT_LIST_HEAD(&skc->skc_emergency_list);
skc->skc_emergency_tree = RB_ROOT;
spin_lock_init(&skc->skc_lock);
init_waitqueue_head(&skc->skc_waitq);
skc->skc_slab_fail = 0;
@@ -1590,7 +1637,6 @@ spl_kmem_cache_destroy(spl_kmem_cache_t *skc)
ASSERT3U(skc->skc_obj_total, ==, 0);
ASSERT3U(skc->skc_obj_emergency, ==, 0);
ASSERT(list_empty(&skc->skc_complete_list));
ASSERT(list_empty(&skc->skc_emergency_list));
kmem_free(skc->skc_name, skc->skc_name_size);
spin_unlock(&skc->skc_lock);