cfq-iosched: get rid of cfqq hash
cfq hash is no more necessary. We always can get cfqq from io context.
cfq_get_io_context_noalloc() function is introduced, because we don't
want to allocate cic on merging and checking may_queue. In order to
identify sync queue we've used hash key = CFQ_KEY_ASYNC. Since hash is
eliminated we need to use other criterion: sync flag for queue is added.
In all places where we dig in rb_tree we're in current context, so no
additional locking is required.
Advantages of this patch: no additional memory for hash, no seeking in
hash, code is cleaner. But it is necessary now to seek cic in per-ioc
rbtree, but it is faster:
- most processes work only with few devices
- most systems have only few block devices
- it is a rb-tree
Signed-off-by: Vasily Tarasov <vtaras@openvz.org>
Changes by me:
- Merge into CFQ devel branch
- Get rid of cfq_get_io_context_noalloc()
- Fix various bugs with dereferencing cic->cfqq[] with offset other
than 0 or 1.
- Fix bug in cfqq setup, is_sync condition was reversed.
- Fix bug where only bio_sync() is used, we need to check for a READ too
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index e859b49..94f53a1 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -9,7 +9,6 @@
#include <linux/module.h>
#include <linux/blkdev.h>
#include <linux/elevator.h>
-#include <linux/hash.h>
#include <linux/rbtree.h>
#include <linux/ioprio.h>
@@ -38,14 +37,6 @@
#define CFQ_SLICE_SCALE (5)
-#define CFQ_KEY_ASYNC (0)
-
-/*
- * for the hash of cfqq inside the cfqd
- */
-#define CFQ_QHASH_SHIFT 6
-#define CFQ_QHASH_ENTRIES (1 << CFQ_QHASH_SHIFT)
-
#define RQ_CIC(rq) ((struct cfq_io_context*)(rq)->elevator_private)
#define RQ_CFQQ(rq) ((rq)->elevator_private2)
@@ -62,8 +53,6 @@
#define ASYNC (0)
#define SYNC (1)
-#define cfq_cfqq_sync(cfqq) ((cfqq)->key != CFQ_KEY_ASYNC)
-
#define sample_valid(samples) ((samples) > 80)
/*
@@ -90,11 +79,6 @@
struct cfq_rb_root service_tree;
unsigned int busy_queues;
- /*
- * cfqq lookup hash
- */
- struct hlist_head *cfq_hash;
-
int rq_in_driver;
int sync_flight;
int hw_tag;
@@ -138,10 +122,6 @@
atomic_t ref;
/* parent cfq_data */
struct cfq_data *cfqd;
- /* cfqq lookup hash */
- struct hlist_node cfq_hash;
- /* hash key */
- unsigned int key;
/* service_tree member */
struct rb_node rb_node;
/* service_tree key */
@@ -186,6 +166,7 @@
CFQ_CFQQ_FLAG_prio_changed, /* task priority has changed */
CFQ_CFQQ_FLAG_queue_new, /* queue never been serviced */
CFQ_CFQQ_FLAG_slice_new, /* no requests dispatched in slice */
+ CFQ_CFQQ_FLAG_sync, /* synchronous queue */
};
#define CFQ_CFQQ_FNS(name) \
@@ -212,11 +193,38 @@
CFQ_CFQQ_FNS(prio_changed);
CFQ_CFQQ_FNS(queue_new);
CFQ_CFQQ_FNS(slice_new);
+CFQ_CFQQ_FNS(sync);
#undef CFQ_CFQQ_FNS
-static struct cfq_queue *cfq_find_cfq_hash(struct cfq_data *, unsigned int, unsigned short);
static void cfq_dispatch_insert(request_queue_t *, struct request *);
-static struct cfq_queue *cfq_get_queue(struct cfq_data *, unsigned int, struct task_struct *, gfp_t);
+static struct cfq_queue *cfq_get_queue(struct cfq_data *, int,
+ struct task_struct *, gfp_t);
+static struct cfq_io_context *cfq_cic_rb_lookup(struct cfq_data *,
+ struct io_context *);
+
+static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic,
+ int is_sync)
+{
+ return cic->cfqq[!!is_sync];
+}
+
+static inline void cic_set_cfqq(struct cfq_io_context *cic,
+ struct cfq_queue *cfqq, int is_sync)
+{
+ cic->cfqq[!!is_sync] = cfqq;
+}
+
+/*
+ * We regard a request as SYNC, if it's either a read or has the SYNC bit
+ * set (in which case it could also be direct WRITE).
+ */
+static inline int cfq_bio_sync(struct bio *bio)
+{
+ if (bio_data_dir(bio) == READ || bio_sync(bio))
+ return 1;
+
+ return 0;
+}
/*
* scheduler run of queue, if there are requests pending and no one in the
@@ -235,17 +243,6 @@
return !cfqd->busy_queues;
}
-static inline pid_t cfq_queue_pid(struct task_struct *task, int rw, int is_sync)
-{
- /*
- * Use the per-process queue, for read requests and syncronous writes
- */
- if (!(rw & REQ_RW) || is_sync)
- return task->pid;
-
- return CFQ_KEY_ASYNC;
-}
-
/*
* Scale schedule slice based on io priority. Use the sync time slice only
* if a queue is marked sync and has sync io queued. A sync queue with async
@@ -608,10 +605,14 @@
cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
{
struct task_struct *tsk = current;
- pid_t key = cfq_queue_pid(tsk, bio_data_dir(bio), bio_sync(bio));
+ struct cfq_io_context *cic;
struct cfq_queue *cfqq;
- cfqq = cfq_find_cfq_hash(cfqd, key, tsk->ioprio);
+ cic = cfq_cic_rb_lookup(cfqd, tsk->io_context);
+ if (!cic)
+ return NULL;
+
+ cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
if (cfqq) {
sector_t sector = bio->bi_sector + bio_sectors(bio);
@@ -705,23 +706,24 @@
struct bio *bio)
{
struct cfq_data *cfqd = q->elevator->elevator_data;
- const int rw = bio_data_dir(bio);
+ struct cfq_io_context *cic;
struct cfq_queue *cfqq;
- pid_t key;
/*
* Disallow merge of a sync bio into an async request.
*/
- if ((bio_data_dir(bio) == READ || bio_sync(bio)) && !rq_is_sync(rq))
+ if (cfq_bio_sync(bio) && !rq_is_sync(rq))
return 0;
/*
* Lookup the cfqq that this bio will be queued with. Allow
* merge only if rq is queued there.
*/
- key = cfq_queue_pid(current, rw, bio_sync(bio));
- cfqq = cfq_find_cfq_hash(cfqd, key, current->ioprio);
+ cic = cfq_cic_rb_lookup(cfqd, current->io_context);
+ if (!cic)
+ return 0;
+ cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
if (cfqq == RQ_CFQQ(rq))
return 1;
@@ -1154,37 +1156,9 @@
cfq_schedule_dispatch(cfqd);
}
- /*
- * it's on the empty list and still hashed
- */
- hlist_del(&cfqq->cfq_hash);
kmem_cache_free(cfq_pool, cfqq);
}
-static struct cfq_queue *
-__cfq_find_cfq_hash(struct cfq_data *cfqd, unsigned int key, unsigned int prio,
- const int hashval)
-{
- struct hlist_head *hash_list = &cfqd->cfq_hash[hashval];
- struct hlist_node *entry;
- struct cfq_queue *__cfqq;
-
- hlist_for_each_entry(__cfqq, entry, hash_list, cfq_hash) {
- const unsigned short __p = IOPRIO_PRIO_VALUE(__cfqq->org_ioprio_class, __cfqq->org_ioprio);
-
- if (__cfqq->key == key && (__p == prio || !prio))
- return __cfqq;
- }
-
- return NULL;
-}
-
-static struct cfq_queue *
-cfq_find_cfq_hash(struct cfq_data *cfqd, unsigned int key, unsigned short prio)
-{
- return __cfq_find_cfq_hash(cfqd, key, prio, hash_long(key, CFQ_QHASH_SHIFT));
-}
-
static void cfq_free_io_context(struct io_context *ioc)
{
struct cfq_io_context *__cic;
@@ -1342,7 +1316,7 @@
cfqq = cic->cfqq[ASYNC];
if (cfqq) {
struct cfq_queue *new_cfqq;
- new_cfqq = cfq_get_queue(cfqd, CFQ_KEY_ASYNC, cic->ioc->task,
+ new_cfqq = cfq_get_queue(cfqd, ASYNC, cic->ioc->task,
GFP_ATOMIC);
if (new_cfqq) {
cic->cfqq[ASYNC] = new_cfqq;
@@ -1374,16 +1348,16 @@
}
static struct cfq_queue *
-cfq_get_queue(struct cfq_data *cfqd, unsigned int key, struct task_struct *tsk,
+cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct task_struct *tsk,
gfp_t gfp_mask)
{
- const int hashval = hash_long(key, CFQ_QHASH_SHIFT);
struct cfq_queue *cfqq, *new_cfqq = NULL;
- unsigned short ioprio;
+ struct cfq_io_context *cic;
retry:
- ioprio = tsk->ioprio;
- cfqq = __cfq_find_cfq_hash(cfqd, key, ioprio, hashval);
+ cic = cfq_cic_rb_lookup(cfqd, tsk->io_context);
+ /* cic always exists here */
+ cfqq = cic_to_cfqq(cic, is_sync);
if (!cfqq) {
if (new_cfqq) {
@@ -1408,20 +1382,20 @@
memset(cfqq, 0, sizeof(*cfqq));
- INIT_HLIST_NODE(&cfqq->cfq_hash);
RB_CLEAR_NODE(&cfqq->rb_node);
INIT_LIST_HEAD(&cfqq->fifo);
- cfqq->key = key;
- hlist_add_head(&cfqq->cfq_hash, &cfqd->cfq_hash[hashval]);
atomic_set(&cfqq->ref, 0);
cfqq->cfqd = cfqd;
- if (key != CFQ_KEY_ASYNC)
+ if (is_sync) {
cfq_mark_cfqq_idle_window(cfqq);
+ cfq_mark_cfqq_sync(cfqq);
+ }
cfq_mark_cfqq_prio_changed(cfqq);
cfq_mark_cfqq_queue_new(cfqq);
+
cfq_init_prio_data(cfqq);
}
@@ -1453,6 +1427,9 @@
struct cfq_io_context *cic;
void *k, *key = cfqd;
+ if (unlikely(!ioc))
+ return NULL;
+
restart:
n = ioc->cic_root.rb_node;
while (n) {
@@ -1839,10 +1816,8 @@
{
struct cfq_data *cfqd = q->elevator->elevator_data;
struct task_struct *tsk = current;
+ struct cfq_io_context *cic;
struct cfq_queue *cfqq;
- unsigned int key;
-
- key = cfq_queue_pid(tsk, rw, rw & REQ_RW_SYNC);
/*
* don't force setup of a queue from here, as a call to may_queue
@@ -1850,7 +1825,11 @@
* so just lookup a possibly existing queue, or return 'may queue'
* if that fails
*/
- cfqq = cfq_find_cfq_hash(cfqd, key, tsk->ioprio);
+ cic = cfq_cic_rb_lookup(cfqd, tsk->io_context);
+ if (!cic)
+ return ELV_MQUEUE_MAY;
+
+ cfqq = cic_to_cfqq(cic, rw & REQ_RW_SYNC);
if (cfqq) {
cfq_init_prio_data(cfqq);
cfq_prio_boost(cfqq);
@@ -1894,7 +1873,6 @@
struct cfq_io_context *cic;
const int rw = rq_data_dir(rq);
const int is_sync = rq_is_sync(rq);
- pid_t key = cfq_queue_pid(tsk, rw, is_sync);
struct cfq_queue *cfqq;
unsigned long flags;
@@ -1907,14 +1885,15 @@
if (!cic)
goto queue_fail;
- if (!cic->cfqq[is_sync]) {
- cfqq = cfq_get_queue(cfqd, key, tsk, gfp_mask);
+ cfqq = cic_to_cfqq(cic, is_sync);
+ if (!cfqq) {
+ cfqq = cfq_get_queue(cfqd, is_sync, tsk, gfp_mask);
+
if (!cfqq)
goto queue_fail;
- cic->cfqq[is_sync] = cfqq;
- } else
- cfqq = cic->cfqq[is_sync];
+ cic_set_cfqq(cic, cfqq, is_sync);
+ }
cfqq->allocated[rw]++;
cfq_clear_cfqq_must_alloc(cfqq);
@@ -2044,14 +2023,12 @@
cfq_shutdown_timer_wq(cfqd);
- kfree(cfqd->cfq_hash);
kfree(cfqd);
}
static void *cfq_init_queue(request_queue_t *q)
{
struct cfq_data *cfqd;
- int i;
cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL, q->node);
if (!cfqd)
@@ -2062,13 +2039,6 @@
cfqd->service_tree = CFQ_RB_ROOT;
INIT_LIST_HEAD(&cfqd->cic_list);
- cfqd->cfq_hash = kmalloc_node(sizeof(struct hlist_head) * CFQ_QHASH_ENTRIES, GFP_KERNEL, q->node);
- if (!cfqd->cfq_hash)
- goto out_free;
-
- for (i = 0; i < CFQ_QHASH_ENTRIES; i++)
- INIT_HLIST_HEAD(&cfqd->cfq_hash[i]);
-
cfqd->queue = q;
init_timer(&cfqd->idle_slice_timer);
@@ -2092,9 +2062,6 @@
cfqd->cfq_slice_idle = cfq_slice_idle;
return cfqd;
-out_free:
- kfree(cfqd);
- return NULL;
}
static void cfq_slab_kill(void)
