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authorJens Axboe <axboe@kernel.dk>2021-02-19 12:33:30 -0700
committerJens Axboe <axboe@kernel.dk>2021-02-25 09:23:47 -0700
commite941894eae31b52f0fd9bdb3ce20620afa152f45 (patch)
treed8705880ec0fa73973f5c243b91986ca23e6ad09 /fs
parenteb2de9418d56b5e6ebf27bad51dbce3e22ee109b (diff)
io-wq: make buffered file write hashed work map per-ctx
Before the io-wq thread change, we maintained a hash work map and lock per-node per-ring. That wasn't ideal, as we really wanted it to be per ring. But now that we have per-task workers, the hash map ends up being just per-task. That'll work just fine for the normal case of having one task use a ring, but if you share the ring between tasks, then it's considerably worse than it was before. Make the hash map per ctx instead, which provides full per-ctx buffered write serialization on hashed writes. Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'fs')
-rw-r--r--fs/io-wq.c85
-rw-r--r--fs/io-wq.h14
-rw-r--r--fs/io_uring.c19
3 files changed, 107 insertions, 11 deletions
diff --git a/fs/io-wq.c b/fs/io-wq.c
index a53df2b3762a..d28ad66b7f16 100644
--- a/fs/io-wq.c
+++ b/fs/io-wq.c
@@ -87,7 +87,6 @@ struct io_wqe {
struct {
raw_spinlock_t lock;
struct io_wq_work_list work_list;
- unsigned long hash_map;
unsigned flags;
} ____cacheline_aligned_in_smp;
@@ -97,6 +96,8 @@ struct io_wqe {
struct hlist_nulls_head free_list;
struct list_head all_list;
+ struct wait_queue_entry wait;
+
struct io_wq *wq;
struct io_wq_work *hash_tail[IO_WQ_NR_HASH_BUCKETS];
};
@@ -113,6 +114,9 @@ struct io_wq {
struct task_struct *manager;
struct user_struct *user;
+
+ struct io_wq_hash *hash;
+
refcount_t refs;
struct completion done;
@@ -328,14 +332,31 @@ static inline unsigned int io_get_work_hash(struct io_wq_work *work)
return work->flags >> IO_WQ_HASH_SHIFT;
}
+static void io_wait_on_hash(struct io_wqe *wqe, unsigned int hash)
+{
+ struct io_wq *wq = wqe->wq;
+
+ spin_lock(&wq->hash->wait.lock);
+ if (list_empty(&wqe->wait.entry)) {
+ __add_wait_queue(&wq->hash->wait, &wqe->wait);
+ if (!test_bit(hash, &wq->hash->map)) {
+ __set_current_state(TASK_RUNNING);
+ list_del_init(&wqe->wait.entry);
+ }
+ }
+ spin_unlock(&wq->hash->wait.lock);
+}
+
static struct io_wq_work *io_get_next_work(struct io_wqe *wqe)
__must_hold(wqe->lock)
{
struct io_wq_work_node *node, *prev;
struct io_wq_work *work, *tail;
- unsigned int hash;
+ unsigned int stall_hash = -1U;
wq_list_for_each(node, prev, &wqe->work_list) {
+ unsigned int hash;
+
work = container_of(node, struct io_wq_work, list);
/* not hashed, can run anytime */
@@ -344,16 +365,26 @@ static struct io_wq_work *io_get_next_work(struct io_wqe *wqe)
return work;
}
- /* hashed, can run if not already running */
hash = io_get_work_hash(work);
- if (!(wqe->hash_map & BIT(hash))) {
- wqe->hash_map |= BIT(hash);
- /* all items with this hash lie in [work, tail] */
- tail = wqe->hash_tail[hash];
+ /* all items with this hash lie in [work, tail] */
+ tail = wqe->hash_tail[hash];
+
+ /* hashed, can run if not already running */
+ if (!test_and_set_bit(hash, &wqe->wq->hash->map)) {
wqe->hash_tail[hash] = NULL;
wq_list_cut(&wqe->work_list, &tail->list, prev);
return work;
}
+ if (stall_hash == -1U)
+ stall_hash = hash;
+ /* fast forward to a next hash, for-each will fix up @prev */
+ node = &tail->list;
+ }
+
+ if (stall_hash != -1U) {
+ raw_spin_unlock(&wqe->lock);
+ io_wait_on_hash(wqe, stall_hash);
+ raw_spin_lock(&wqe->lock);
}
return NULL;
@@ -421,6 +452,7 @@ get_next:
if (!work)
break;
io_assign_current_work(worker, work);
+ __set_current_state(TASK_RUNNING);
/* handle a whole dependent link */
do {
@@ -444,8 +476,10 @@ get_next:
io_wqe_enqueue(wqe, linked);
if (hash != -1U && !next_hashed) {
+ clear_bit(hash, &wq->hash->map);
+ if (wq_has_sleeper(&wq->hash->wait))
+ wake_up(&wq->hash->wait);
raw_spin_lock_irq(&wqe->lock);
- wqe->hash_map &= ~BIT_ULL(hash);
wqe->flags &= ~IO_WQE_FLAG_STALLED;
/* skip unnecessary unlock-lock wqe->lock */
if (!work)
@@ -471,7 +505,6 @@ static int io_wqe_worker(void *data)
loop:
raw_spin_lock_irq(&wqe->lock);
if (io_wqe_run_queue(wqe)) {
- __set_current_state(TASK_RUNNING);
io_worker_handle_work(worker);
goto loop;
}
@@ -928,6 +961,24 @@ enum io_wq_cancel io_wq_cancel_cb(struct io_wq *wq, work_cancel_fn *cancel,
return IO_WQ_CANCEL_NOTFOUND;
}
+static int io_wqe_hash_wake(struct wait_queue_entry *wait, unsigned mode,
+ int sync, void *key)
+{
+ struct io_wqe *wqe = container_of(wait, struct io_wqe, wait);
+ int ret;
+
+ list_del_init(&wait->entry);
+
+ rcu_read_lock();
+ ret = io_wqe_activate_free_worker(wqe);
+ rcu_read_unlock();
+
+ if (!ret)
+ wake_up_process(wqe->wq->manager);
+
+ return 1;
+}
+
struct io_wq *io_wq_create(unsigned bounded, struct io_wq_data *data)
{
int ret = -ENOMEM, node;
@@ -948,6 +999,8 @@ struct io_wq *io_wq_create(unsigned bounded, struct io_wq_data *data)
if (ret)
goto err_wqes;
+ refcount_inc(&data->hash->refs);
+ wq->hash = data->hash;
wq->free_work = data->free_work;
wq->do_work = data->do_work;
@@ -968,6 +1021,8 @@ struct io_wq *io_wq_create(unsigned bounded, struct io_wq_data *data)
wqe->acct[IO_WQ_ACCT_UNBOUND].max_workers =
task_rlimit(current, RLIMIT_NPROC);
atomic_set(&wqe->acct[IO_WQ_ACCT_UNBOUND].nr_running, 0);
+ wqe->wait.func = io_wqe_hash_wake;
+ INIT_LIST_HEAD(&wqe->wait.entry);
wqe->wq = wq;
raw_spin_lock_init(&wqe->lock);
INIT_WQ_LIST(&wqe->work_list);
@@ -989,6 +1044,7 @@ struct io_wq *io_wq_create(unsigned bounded, struct io_wq_data *data)
if (refcount_dec_and_test(&wq->refs))
complete(&wq->done);
+ io_wq_put_hash(data->hash);
err:
cpuhp_state_remove_instance_nocalls(io_wq_online, &wq->cpuhp_node);
for_each_node(node)
@@ -1017,8 +1073,15 @@ void io_wq_destroy(struct io_wq *wq)
wait_for_completion(&wq->done);
- for_each_node(node)
- kfree(wq->wqes[node]);
+ spin_lock_irq(&wq->hash->wait.lock);
+ for_each_node(node) {
+ struct io_wqe *wqe = wq->wqes[node];
+
+ list_del_init(&wqe->wait.entry);
+ kfree(wqe);
+ }
+ spin_unlock_irq(&wq->hash->wait.lock);
+ io_wq_put_hash(wq->hash);
kfree(wq->wqes);
kfree(wq);
}
diff --git a/fs/io-wq.h b/fs/io-wq.h
index 86825673be08..3677b39db015 100644
--- a/fs/io-wq.h
+++ b/fs/io-wq.h
@@ -1,6 +1,7 @@
#ifndef INTERNAL_IO_WQ_H
#define INTERNAL_IO_WQ_H
+#include <linux/refcount.h>
#include <linux/io_uring.h>
struct io_wq;
@@ -93,7 +94,20 @@ static inline struct io_wq_work *wq_next_work(struct io_wq_work *work)
typedef struct io_wq_work *(free_work_fn)(struct io_wq_work *);
typedef void (io_wq_work_fn)(struct io_wq_work *);
+struct io_wq_hash {
+ refcount_t refs;
+ unsigned long map;
+ struct wait_queue_head wait;
+};
+
+static inline void io_wq_put_hash(struct io_wq_hash *hash)
+{
+ if (refcount_dec_and_test(&hash->refs))
+ kfree(hash);
+}
+
struct io_wq_data {
+ struct io_wq_hash *hash;
io_wq_work_fn *do_work;
free_work_fn *free_work;
};
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 0a435a6f265a..fbc85afa9a87 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -360,6 +360,9 @@ struct io_ring_ctx {
unsigned cached_cq_overflow;
unsigned long sq_check_overflow;
+ /* hashed buffered write serialization */
+ struct io_wq_hash *hash_map;
+
struct list_head defer_list;
struct list_head timeout_list;
struct list_head cq_overflow_list;
@@ -454,6 +457,8 @@ struct io_ring_ctx {
/* exit task_work */
struct callback_head *exit_task_work;
+ struct wait_queue_head hash_wait;
+
/* Keep this last, we don't need it for the fast path */
struct work_struct exit_work;
};
@@ -7763,9 +7768,21 @@ static struct io_wq_work *io_free_work(struct io_wq_work *work)
static struct io_wq *io_init_wq_offload(struct io_ring_ctx *ctx)
{
+ struct io_wq_hash *hash;
struct io_wq_data data;
unsigned int concurrency;
+ hash = ctx->hash_map;
+ if (!hash) {
+ hash = kzalloc(sizeof(*hash), GFP_KERNEL);
+ if (!hash)
+ return ERR_PTR(-ENOMEM);
+ refcount_set(&hash->refs, 1);
+ init_waitqueue_head(&hash->wait);
+ ctx->hash_map = hash;
+ }
+
+ data.hash = hash;
data.free_work = io_free_work;
data.do_work = io_wq_submit_work;
@@ -8405,6 +8422,8 @@ static void io_ring_ctx_free(struct io_ring_ctx *ctx)
percpu_ref_exit(&ctx->refs);
free_uid(ctx->user);
io_req_caches_free(ctx, NULL);
+ if (ctx->hash_map)
+ io_wq_put_hash(ctx->hash_map);
kfree(ctx->cancel_hash);
kfree(ctx);
}