This is a note to let you know that I've just added the patch titled
io_uring/napi: use ktime in busy polling
to the 6.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
io_uring-napi-use-ktime-in-busy-polling.patch
and it can be found in the queue-6.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 4ee14031d88066739185950822fa796ce41c1024
Author: Pavel Begunkov <asml.silence@xxxxxxxxx>
Date: Fri Jul 26 15:24:30 2024 +0100
io_uring/napi: use ktime in busy polling
[ Upstream commit 342b2e395d5f34c9f111a818556e617939f83a8c ]
It's more natural to use ktime/ns instead of keeping around usec,
especially since we're comparing it against user provided timers,
so convert napi busy poll internal handling to ktime. It's also nicer
since the type (ktime_t vs unsigned long) now tells the unit of measure.
Keep everything as ktime, which we convert to/from micro seconds for
IORING_[UN]REGISTER_NAPI. The net/ busy polling works seems to work with
usec, however it's not real usec as shift by 10 is used to get it from
nsecs, see busy_loop_current_time(), so it's easy to get truncated nsec
back and we get back better precision.
Note, we can further improve it later by removing the truncation and
maybe convincing net/ to use ktime/ns instead.
Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
Link: https://lore.kernel.org/r/95e7ec8d095069a3ed5d40a4bc6f8b586698bc7e.1722003776.git.asml.silence@xxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Stable-dep-of: 84f2eecf9501 ("io_uring/napi: check napi_enabled in io_napi_add() before proceeding")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/include/linux/io_uring_types.h b/include/linux/io_uring_types.h
index 7abdc09271245..b18e998c8b887 100644
--- a/include/linux/io_uring_types.h
+++ b/include/linux/io_uring_types.h
@@ -410,7 +410,7 @@ struct io_ring_ctx {
spinlock_t napi_lock; /* napi_list lock */
/* napi busy poll default timeout */
- unsigned int napi_busy_poll_to;
+ ktime_t napi_busy_poll_dt;
bool napi_prefer_busy_poll;
bool napi_enabled;
diff --git a/io_uring/io_uring.h b/io_uring/io_uring.h
index 726e6367af4d3..af46d03d58847 100644
--- a/io_uring/io_uring.h
+++ b/io_uring/io_uring.h
@@ -43,7 +43,7 @@ struct io_wait_queue {
ktime_t timeout;
#ifdef CONFIG_NET_RX_BUSY_POLL
- unsigned int napi_busy_poll_to;
+ ktime_t napi_busy_poll_dt;
bool napi_prefer_busy_poll;
#endif
};
diff --git a/io_uring/napi.c b/io_uring/napi.c
index 327e5f3a8abe0..6bdb267e9c33c 100644
--- a/io_uring/napi.c
+++ b/io_uring/napi.c
@@ -33,6 +33,12 @@ static struct io_napi_entry *io_napi_hash_find(struct hlist_head *hash_list,
return NULL;
}
+static inline ktime_t net_to_ktime(unsigned long t)
+{
+ /* napi approximating usecs, reverse busy_loop_current_time */
+ return ns_to_ktime(t << 10);
+}
+
void __io_napi_add(struct io_ring_ctx *ctx, struct socket *sock)
{
struct hlist_head *hash_list;
@@ -102,14 +108,14 @@ static inline void io_napi_remove_stale(struct io_ring_ctx *ctx, bool is_stale)
__io_napi_remove_stale(ctx);
}
-static inline bool io_napi_busy_loop_timeout(unsigned long start_time,
- unsigned long bp_usec)
+static inline bool io_napi_busy_loop_timeout(ktime_t start_time,
+ ktime_t bp)
{
- if (bp_usec) {
- unsigned long end_time = start_time + bp_usec;
- unsigned long now = busy_loop_current_time();
+ if (bp) {
+ ktime_t end_time = ktime_add(start_time, bp);
+ ktime_t now = net_to_ktime(busy_loop_current_time());
- return time_after(now, end_time);
+ return ktime_after(now, end_time);
}
return true;
@@ -124,7 +130,8 @@ static bool io_napi_busy_loop_should_end(void *data,
return true;
if (io_should_wake(iowq) || io_has_work(iowq->ctx))
return true;
- if (io_napi_busy_loop_timeout(start_time, iowq->napi_busy_poll_to))
+ if (io_napi_busy_loop_timeout(net_to_ktime(start_time),
+ iowq->napi_busy_poll_dt))
return true;
return false;
@@ -181,10 +188,12 @@ static void io_napi_blocking_busy_loop(struct io_ring_ctx *ctx,
*/
void io_napi_init(struct io_ring_ctx *ctx)
{
+ u64 sys_dt = READ_ONCE(sysctl_net_busy_poll) * NSEC_PER_USEC;
+
INIT_LIST_HEAD(&ctx->napi_list);
spin_lock_init(&ctx->napi_lock);
ctx->napi_prefer_busy_poll = false;
- ctx->napi_busy_poll_to = READ_ONCE(sysctl_net_busy_poll);
+ ctx->napi_busy_poll_dt = ns_to_ktime(sys_dt);
}
/*
@@ -217,7 +226,7 @@ void io_napi_free(struct io_ring_ctx *ctx)
int io_register_napi(struct io_ring_ctx *ctx, void __user *arg)
{
const struct io_uring_napi curr = {
- .busy_poll_to = ctx->napi_busy_poll_to,
+ .busy_poll_to = ktime_to_us(ctx->napi_busy_poll_dt),
.prefer_busy_poll = ctx->napi_prefer_busy_poll
};
struct io_uring_napi napi;
@@ -232,7 +241,7 @@ int io_register_napi(struct io_ring_ctx *ctx, void __user *arg)
if (copy_to_user(arg, &curr, sizeof(curr)))
return -EFAULT;
- WRITE_ONCE(ctx->napi_busy_poll_to, napi.busy_poll_to);
+ WRITE_ONCE(ctx->napi_busy_poll_dt, napi.busy_poll_to * NSEC_PER_USEC);
WRITE_ONCE(ctx->napi_prefer_busy_poll, !!napi.prefer_busy_poll);
WRITE_ONCE(ctx->napi_enabled, true);
return 0;
@@ -249,14 +258,14 @@ int io_register_napi(struct io_ring_ctx *ctx, void __user *arg)
int io_unregister_napi(struct io_ring_ctx *ctx, void __user *arg)
{
const struct io_uring_napi curr = {
- .busy_poll_to = ctx->napi_busy_poll_to,
+ .busy_poll_to = ktime_to_us(ctx->napi_busy_poll_dt),
.prefer_busy_poll = ctx->napi_prefer_busy_poll
};
if (arg && copy_to_user(arg, &curr, sizeof(curr)))
return -EFAULT;
- WRITE_ONCE(ctx->napi_busy_poll_to, 0);
+ WRITE_ONCE(ctx->napi_busy_poll_dt, 0);
WRITE_ONCE(ctx->napi_prefer_busy_poll, false);
WRITE_ONCE(ctx->napi_enabled, false);
return 0;
@@ -275,23 +284,20 @@ int io_unregister_napi(struct io_ring_ctx *ctx, void __user *arg)
void __io_napi_adjust_timeout(struct io_ring_ctx *ctx, struct io_wait_queue *iowq,
struct timespec64 *ts)
{
- unsigned int poll_to = READ_ONCE(ctx->napi_busy_poll_to);
+ ktime_t poll_dt = READ_ONCE(ctx->napi_busy_poll_dt);
if (ts) {
struct timespec64 poll_to_ts;
- poll_to_ts = ns_to_timespec64(1000 * (s64)poll_to);
+ poll_to_ts = ns_to_timespec64(ktime_to_ns(poll_dt));
if (timespec64_compare(ts, &poll_to_ts) < 0) {
s64 poll_to_ns = timespec64_to_ns(ts);
- if (poll_to_ns > 0) {
- u64 val = poll_to_ns + 999;
- do_div(val, 1000);
- poll_to = val;
- }
+ if (poll_to_ns > 0)
+ poll_dt = ns_to_ktime(poll_to_ns);
}
}
- iowq->napi_busy_poll_to = poll_to;
+ iowq->napi_busy_poll_dt = poll_dt;
}
/*
@@ -320,7 +326,7 @@ int io_napi_sqpoll_busy_poll(struct io_ring_ctx *ctx)
LIST_HEAD(napi_list);
bool is_stale = false;
- if (!READ_ONCE(ctx->napi_busy_poll_to))
+ if (!READ_ONCE(ctx->napi_busy_poll_dt))
return 0;
if (list_empty_careful(&ctx->napi_list))
return 0;
diff --git a/io_uring/napi.h b/io_uring/napi.h
index 6fc0393d0dbef..babbee36cd3eb 100644
--- a/io_uring/napi.h
+++ b/io_uring/napi.h
@@ -55,7 +55,7 @@ static inline void io_napi_add(struct io_kiocb *req)
struct io_ring_ctx *ctx = req->ctx;
struct socket *sock;
- if (!READ_ONCE(ctx->napi_busy_poll_to))
+ if (!READ_ONCE(ctx->napi_busy_poll_dt))
return;
sock = sock_from_file(req->file);
