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io_uring: remove priority tw list optimisation

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This optimisation has some built in assumptions that make it easy to
introduce bugs. It also does not have clear wins that make it worth keeping.

Signed-off-by: Dylan Yudaken <dylany@fb.com>
Link: https://lore.kernel.org/r/20220622134028.2013417-2-dylany@fb.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Dylan Yudaken 2022-06-22 06:40:21 -07:00 committed by Jens Axboe
parent 024f15e033
commit ed5ccb3bee
5 changed files with 12 additions and 70 deletions
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77
io_uring/io_uring.c
View File

@ -986,44 +986,6 @@ static void ctx_flush_and_put(struct io_ring_ctx *ctx, bool *locked)
percpu_ref_put(&ctx->refs);
}
static void handle_prev_tw_list(struct io_wq_work_node *node,
struct io_ring_ctx **ctx, bool *uring_locked)
{
if (*ctx && !*uring_locked)
spin_lock(&(*ctx)->completion_lock);
do {
struct io_wq_work_node *next = node->next;
struct io_kiocb *req = container_of(node, struct io_kiocb,
io_task_work.node);
prefetch(container_of(next, struct io_kiocb, io_task_work.node));
if (req->ctx != *ctx) {
if (unlikely(!*uring_locked && *ctx))
io_cq_unlock_post(*ctx);
ctx_flush_and_put(*ctx, uring_locked);
*ctx = req->ctx;
/* if not contended, grab and improve batching */
*uring_locked = mutex_trylock(&(*ctx)->uring_lock);
percpu_ref_get(&(*ctx)->refs);
if (unlikely(!*uring_locked))
io_cq_lock(*ctx);
}
if (likely(*uring_locked)) {
req->io_task_work.func(req, uring_locked);
} else {
req->cqe.flags = io_put_kbuf_comp(req);
__io_req_complete_post(req);
}
node = next;
} while (node);
if (unlikely(!*uring_locked))
io_cq_unlock_post(*ctx);
}
static void handle_tw_list(struct io_wq_work_node *node,
struct io_ring_ctx **ctx, bool *locked)
{
@ -1054,27 +1016,20 @@ void tctx_task_work(struct callback_head *cb)
task_work);
while (1) {
struct io_wq_work_node *node1, *node2;
struct io_wq_work_node *node;
spin_lock_irq(&tctx->task_lock);
node1 = tctx->prio_task_list.first;
node2 = tctx->task_list.first;
node = tctx->task_list.first;
INIT_WQ_LIST(&tctx->task_list);
INIT_WQ_LIST(&tctx->prio_task_list);
if (!node2 && !node1)
if (!node)
tctx->task_running = false;
spin_unlock_irq(&tctx->task_lock);
if (!node2 && !node1)
if (!node)
break;
if (node1)
handle_prev_tw_list(node1, &ctx, &uring_locked);
if (node2)
handle_tw_list(node2, &ctx, &uring_locked);
handle_tw_list(node, &ctx, &uring_locked);
cond_resched();
if (data_race(!tctx->task_list.first) &&
data_race(!tctx->prio_task_list.first) && uring_locked)
if (data_race(!tctx->task_list.first) && uring_locked)
io_submit_flush_completions(ctx);
}
@ -1086,8 +1041,7 @@ void tctx_task_work(struct callback_head *cb)
}
static void __io_req_task_work_add(struct io_kiocb *req,
struct io_uring_task *tctx,
struct io_wq_work_list *list)
struct io_uring_task *tctx)
{
struct io_ring_ctx *ctx = req->ctx;
struct io_wq_work_node *node;
@ -1095,7 +1049,7 @@ static void __io_req_task_work_add(struct io_kiocb *req,
bool running;
spin_lock_irqsave(&tctx->task_lock, flags);
wq_list_add_tail(&req->io_task_work.node, list);
wq_list_add_tail(&req->io_task_work.node, &tctx->task_list);
running = tctx->task_running;
if (!running)
tctx->task_running = true;
@ -1113,7 +1067,8 @@ static void __io_req_task_work_add(struct io_kiocb *req,
spin_lock_irqsave(&tctx->task_lock, flags);
tctx->task_running = false;
node = wq_list_merge(&tctx->prio_task_list, &tctx->task_list);
node = tctx->task_list.first;
INIT_WQ_LIST(&tctx->task_list);
spin_unlock_irqrestore(&tctx->task_lock, flags);
while (node) {
@ -1129,17 +1084,7 @@ void io_req_task_work_add(struct io_kiocb *req)
{
struct io_uring_task *tctx = req->task->io_uring;
__io_req_task_work_add(req, tctx, &tctx->task_list);
}
void io_req_task_prio_work_add(struct io_kiocb *req)
{
struct io_uring_task *tctx = req->task->io_uring;
if (req->ctx->flags & IORING_SETUP_SQPOLL)
__io_req_task_work_add(req, tctx, &tctx->prio_task_list);
else
__io_req_task_work_add(req, tctx, &tctx->task_list);
__io_req_task_work_add(req, tctx);
}
static void io_req_tw_post(struct io_kiocb *req, bool *locked)

1
io_uring/io_uring.h
View File

@ -36,7 +36,6 @@ struct file *io_file_get_fixed(struct io_kiocb *req, int fd,
bool io_is_uring_fops(struct file *file);
bool io_alloc_async_data(struct io_kiocb *req);
void io_req_task_work_add(struct io_kiocb *req);
void io_req_task_prio_work_add(struct io_kiocb *req);
void io_req_tw_post_queue(struct io_kiocb *req, s32 res, u32 cflags);
void io_req_task_queue(struct io_kiocb *req);
void io_queue_iowq(struct io_kiocb *req, bool *dont_use);

2
io_uring/rw.c
View File

@ -215,7 +215,7 @@ static void io_complete_rw(struct kiocb *kiocb, long res)
return;
io_req_set_res(req, res, 0);
req->io_task_work.func = io_req_task_complete;
io_req_task_prio_work_add(req);
io_req_task_work_add(req);
}
static void io_complete_rw_iopoll(struct kiocb *kiocb, long res)

1
io_uring/tctx.c
View File

@ -88,7 +88,6 @@ __cold int io_uring_alloc_task_context(struct task_struct *task,
task->io_uring = tctx;
spin_lock_init(&tctx->task_lock);
INIT_WQ_LIST(&tctx->task_list);
INIT_WQ_LIST(&tctx->prio_task_list);
init_task_work(&tctx->task_work, tctx_task_work);
return 0;
}

1
io_uring/tctx.h
View File

@ -22,7 +22,6 @@ struct io_uring_task {
spinlock_t task_lock;
bool task_running;
struct io_wq_work_list task_list;
struct io_wq_work_list prio_task_list;
struct callback_head task_work;
} ____cacheline_aligned_in_smp;
};