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dm bufio: switch from a huge hash table to an rbtree

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Converting over to using an rbtree eliminates a fixed 8MB allocation
from vmalloc space for the hash table.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Joe Thornber 2014-10-06 13:48:51 +01:00 committed by Mike Snitzer
parent 9b460d3699
commit 4e420c452b
1 changed files with 54 additions and 43 deletions
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97
drivers/md/dm-bufio.c
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@ -14,6 +14,7 @@
#include <linux/vmalloc.h>
#include <linux/shrinker.h>
#include <linux/module.h>
#include <linux/rbtree.h>
#define DM_MSG_PREFIX "bufio"
@ -47,14 +48,6 @@
*/
#define DM_BUFIO_INLINE_VECS 16
/*
* Buffer hash
*/
#define DM_BUFIO_HASH_BITS 20
#define DM_BUFIO_HASH(block) \
((((block) >> DM_BUFIO_HASH_BITS) ^ (block)) & \
((1 << DM_BUFIO_HASH_BITS) - 1))
/*
* Don't try to use kmem_cache_alloc for blocks larger than this.
* For explanation, see alloc_buffer_data below.
@ -106,7 +99,7 @@ struct dm_bufio_client {
unsigned minimum_buffers;
struct hlist_head *cache_hash;
struct rb_root buffer_tree;
wait_queue_head_t free_buffer_wait;
int async_write_error;
@ -135,7 +128,7 @@ enum data_mode {
};
struct dm_buffer {
struct hlist_node hash_list;
struct rb_node node;
struct list_head lru_list;
sector_t block;
void *data;
@ -253,6 +246,53 @@ static LIST_HEAD(dm_bufio_all_clients);
*/
static DEFINE_MUTEX(dm_bufio_clients_lock);
/*----------------------------------------------------------------
* A red/black tree acts as an index for all the buffers.
*--------------------------------------------------------------*/
static struct dm_buffer *__find(struct dm_bufio_client *c, sector_t block)
{
struct rb_node *n = c->buffer_tree.rb_node;
struct dm_buffer *b;
while (n) {
b = container_of(n, struct dm_buffer, node);
if (b->block == block)
return b;
n = (b->block < block) ? n->rb_left : n->rb_right;
}
return NULL;
}
static void __insert(struct dm_bufio_client *c, struct dm_buffer *b)
{
struct rb_node **new = &c->buffer_tree.rb_node, *parent = NULL;
struct dm_buffer *found;
while (*new) {
found = container_of(*new, struct dm_buffer, node);
if (found->block == b->block) {
BUG_ON(found != b);
return;
}
parent = *new;
new = (found->block < b->block) ?
&((*new)->rb_left) : &((*new)->rb_right);
}
rb_link_node(&b->node, parent, new);
rb_insert_color(&b->node, &c->buffer_tree);
}
static void __remove(struct dm_bufio_client *c, struct dm_buffer *b)
{
rb_erase(&b->node, &c->buffer_tree);
}
/*----------------------------------------------------------------*/
static void adjust_total_allocated(enum data_mode data_mode, long diff)
@ -434,7 +474,7 @@ static void __link_buffer(struct dm_buffer *b, sector_t block, int dirty)
b->block = block;
b->list_mode = dirty;
list_add(&b->lru_list, &c->lru[dirty]);
hlist_add_head(&b->hash_list, &c->cache_hash[DM_BUFIO_HASH(block)]);
__insert(b->c, b);
b->last_accessed = jiffies;
}
@ -448,7 +488,7 @@ static void __unlink_buffer(struct dm_buffer *b)
BUG_ON(!c->n_buffers[b->list_mode]);
c->n_buffers[b->list_mode]--;
hlist_del(&b->hash_list);
__remove(b->c, b);
list_del(&b->lru_list);
}
@ -888,23 +928,6 @@ static void __check_watermark(struct dm_bufio_client *c,
__write_dirty_buffers_async(c, 1, write_list);
}
/*
* Find a buffer in the hash.
*/
static struct dm_buffer *__find(struct dm_bufio_client *c, sector_t block)
{
struct dm_buffer *b;
hlist_for_each_entry(b, &c->cache_hash[DM_BUFIO_HASH(block)],
hash_list) {
dm_bufio_cond_resched();
if (b->block == block)
return b;
}
return NULL;
}
/*----------------------------------------------------------------
* Getting a buffer
*--------------------------------------------------------------*/
@ -1534,11 +1557,7 @@ struct dm_bufio_client *dm_bufio_client_create(struct block_device *bdev, unsign
r = -ENOMEM;
goto bad_client;
}
c->cache_hash = vmalloc(sizeof(struct hlist_head) << DM_BUFIO_HASH_BITS);
if (!c->cache_hash) {
r = -ENOMEM;
goto bad_hash;
}
c->buffer_tree = RB_ROOT;
c->bdev = bdev;
c->block_size = block_size;
@ -1557,9 +1576,6 @@ struct dm_bufio_client *dm_bufio_client_create(struct block_device *bdev, unsign
c->n_buffers[i] = 0;
}
for (i = 0; i < 1 << DM_BUFIO_HASH_BITS; i++)
INIT_HLIST_HEAD(&c->cache_hash[i]);
mutex_init(&c->lock);
INIT_LIST_HEAD(&c->reserved_buffers);
c->need_reserved_buffers = reserved_buffers;
@ -1633,8 +1649,6 @@ bad_cache:
}
dm_io_client_destroy(c->dm_io);
bad_dm_io:
vfree(c->cache_hash);
bad_hash:
kfree(c);
bad_client:
return ERR_PTR(r);
@ -1661,9 +1675,7 @@ void dm_bufio_client_destroy(struct dm_bufio_client *c)
mutex_unlock(&dm_bufio_clients_lock);
for (i = 0; i < 1 << DM_BUFIO_HASH_BITS; i++)
BUG_ON(!hlist_empty(&c->cache_hash[i]));
BUG_ON(!RB_EMPTY_ROOT(&c->buffer_tree));
BUG_ON(c->need_reserved_buffers);
while (!list_empty(&c->reserved_buffers)) {
@ -1681,7 +1693,6 @@ void dm_bufio_client_destroy(struct dm_bufio_client *c)
BUG_ON(c->n_buffers[i]);
dm_io_client_destroy(c->dm_io);
vfree(c->cache_hash);
kfree(c);
}
EXPORT_SYMBOL_GPL(dm_bufio_client_destroy);