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Message-ID: <20250128133927.3989681-5-max.kellermann@ionos.com>
Date: Tue, 28 Jan 2025 14:39:23 +0100
From: Max Kellermann <max.kellermann@...os.com>
To: axboe@...nel.dk,
asml.silence@...il.com,
io-uring@...r.kernel.org,
linux-kernel@...r.kernel.org
Cc: Max Kellermann <max.kellermann@...os.com>
Subject: [PATCH 4/8] io_uring/io-wq: cache work->flags in variable
This eliminates several redundant atomic reads and therefore reduces
the duration the surrounding spinlocks are held.
In several io_uring benchmarks, this reduced the CPU time spent in
queued_spin_lock_slowpath() considerably:
io_uring benchmark with a flood of `IORING_OP_NOP` and `IOSQE_ASYNC`:
38.86% -1.49% [kernel.kallsyms] [k] queued_spin_lock_slowpath
6.75% +0.36% [kernel.kallsyms] [k] io_worker_handle_work
2.60% +0.19% [kernel.kallsyms] [k] io_nop
3.92% +0.18% [kernel.kallsyms] [k] io_req_task_complete
6.34% -0.18% [kernel.kallsyms] [k] io_wq_submit_work
HTTP server, static file:
42.79% -2.77% [kernel.kallsyms] [k] queued_spin_lock_slowpath
2.08% +0.23% [kernel.kallsyms] [k] io_wq_submit_work
1.19% +0.20% [kernel.kallsyms] [k] amd_iommu_iotlb_sync_map
1.46% +0.15% [kernel.kallsyms] [k] ep_poll_callback
1.80% +0.15% [kernel.kallsyms] [k] io_worker_handle_work
HTTP server, PHP:
35.03% -1.80% [kernel.kallsyms] [k] queued_spin_lock_slowpath
0.84% +0.21% [kernel.kallsyms] [k] amd_iommu_iotlb_sync_map
1.39% +0.12% [kernel.kallsyms] [k] _copy_to_iter
0.21% +0.10% [kernel.kallsyms] [k] update_sd_lb_stats
Signed-off-by: Max Kellermann <max.kellermann@...os.com>
---
io_uring/io-wq.c | 33 +++++++++++++++++++++------------
io_uring/io-wq.h | 7 ++++++-
2 files changed, 27 insertions(+), 13 deletions(-)
diff --git a/io_uring/io-wq.c b/io_uring/io-wq.c
index dfdd45ebe4bb..ba9974e6f521 100644
--- a/io_uring/io-wq.c
+++ b/io_uring/io-wq.c
@@ -170,9 +170,9 @@ static inline struct io_wq_acct *io_get_acct(struct io_wq *wq, bool bound)
}
static inline struct io_wq_acct *io_work_get_acct(struct io_wq *wq,
- struct io_wq_work *work)
+ unsigned int work_flags)
{
- return io_get_acct(wq, !(atomic_read(&work->flags) & IO_WQ_WORK_UNBOUND));
+ return io_get_acct(wq, !(work_flags & IO_WQ_WORK_UNBOUND));
}
static inline struct io_wq_acct *io_wq_get_acct(struct io_worker *worker)
@@ -457,9 +457,14 @@ static void __io_worker_idle(struct io_wq_acct *acct, struct io_worker *worker)
}
}
+static inline unsigned int __io_get_work_hash(unsigned int work_flags)
+{
+ return work_flags >> IO_WQ_HASH_SHIFT;
+}
+
static inline unsigned int io_get_work_hash(struct io_wq_work *work)
{
- return atomic_read(&work->flags) >> IO_WQ_HASH_SHIFT;
+ return __io_get_work_hash(atomic_read(&work->flags));
}
static bool io_wait_on_hash(struct io_wq *wq, unsigned int hash)
@@ -489,17 +494,19 @@ static struct io_wq_work *io_get_next_work(struct io_wq_acct *acct,
struct io_wq *wq = worker->wq;
wq_list_for_each(node, prev, &acct->work_list) {
+ unsigned int work_flags;
unsigned int hash;
work = container_of(node, struct io_wq_work, list);
/* not hashed, can run anytime */
- if (!io_wq_is_hashed(work)) {
+ work_flags = atomic_read(&work->flags);
+ if (!__io_wq_is_hashed(work_flags)) {
wq_list_del(&acct->work_list, node, prev);
return work;
}
- hash = io_get_work_hash(work);
+ hash = __io_get_work_hash(work_flags);
/* all items with this hash lie in [work, tail] */
tail = wq->hash_tail[hash];
@@ -596,12 +603,13 @@ static void io_worker_handle_work(struct io_wq_acct *acct,
/* handle a whole dependent link */
do {
struct io_wq_work *next_hashed, *linked;
- unsigned int hash = io_get_work_hash(work);
+ unsigned int work_flags = atomic_read(&work->flags);
+ unsigned int hash = __io_get_work_hash(work_flags);
next_hashed = wq_next_work(work);
if (do_kill &&
- (atomic_read(&work->flags) & IO_WQ_WORK_UNBOUND))
+ (work_flags & IO_WQ_WORK_UNBOUND))
atomic_or(IO_WQ_WORK_CANCEL, &work->flags);
wq->do_work(work);
io_assign_current_work(worker, NULL);
@@ -917,18 +925,19 @@ static void io_run_cancel(struct io_wq_work *work, struct io_wq *wq)
} while (work);
}
-static void io_wq_insert_work(struct io_wq *wq, struct io_wq_acct *acct, struct io_wq_work *work)
+static void io_wq_insert_work(struct io_wq *wq, struct io_wq_acct *acct,
+ struct io_wq_work *work, unsigned int work_flags)
{
unsigned int hash;
struct io_wq_work *tail;
- if (!io_wq_is_hashed(work)) {
+ if (!__io_wq_is_hashed(work_flags)) {
append:
wq_list_add_tail(&work->list, &acct->work_list);
return;
}
- hash = io_get_work_hash(work);
+ hash = __io_get_work_hash(work_flags);
tail = wq->hash_tail[hash];
wq->hash_tail[hash] = work;
if (!tail)
@@ -944,8 +953,8 @@ static bool io_wq_work_match_item(struct io_wq_work *work, void *data)
void io_wq_enqueue(struct io_wq *wq, struct io_wq_work *work)
{
- struct io_wq_acct *acct = io_work_get_acct(wq, work);
unsigned int work_flags = atomic_read(&work->flags);
+ struct io_wq_acct *acct = io_work_get_acct(wq, work_flags);
struct io_cb_cancel_data match = {
.fn = io_wq_work_match_item,
.data = work,
@@ -964,7 +973,7 @@ void io_wq_enqueue(struct io_wq *wq, struct io_wq_work *work)
}
raw_spin_lock(&acct->lock);
- io_wq_insert_work(wq, acct, work);
+ io_wq_insert_work(wq, acct, work, work_flags);
clear_bit(IO_ACCT_STALLED_BIT, &acct->flags);
raw_spin_unlock(&acct->lock);
diff --git a/io_uring/io-wq.h b/io_uring/io-wq.h
index b3b004a7b625..d4fb2940e435 100644
--- a/io_uring/io-wq.h
+++ b/io_uring/io-wq.h
@@ -54,9 +54,14 @@ int io_wq_cpu_affinity(struct io_uring_task *tctx, cpumask_var_t mask);
int io_wq_max_workers(struct io_wq *wq, int *new_count);
bool io_wq_worker_stopped(void);
+static inline bool __io_wq_is_hashed(unsigned int work_flags)
+{
+ return work_flags & IO_WQ_WORK_HASHED;
+}
+
static inline bool io_wq_is_hashed(struct io_wq_work *work)
{
- return atomic_read(&work->flags) & IO_WQ_WORK_HASHED;
+ return __io_wq_is_hashed(atomic_read(&work->flags));
}
typedef bool (work_cancel_fn)(struct io_wq_work *, void *);
--
2.45.2
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