[PATCH v2 0/3] napi tracking strategy

[PATCH v2 0/3] napi tracking strategy

[Olivier Langlois]

the actual napi tracking strategy is inducing a non-negligeable overhead.
Everytime a multishot poll is triggered or any poll armed, if the napi is
enabled on the ring a lookup is performed to either add a new napi id into
the napi_list or its timeout value is updated.

For many scenarios, this is overkill as the napi id list will be pretty
much static most of the time. To address this common scenario, a new
abstraction has been created following the common Linux kernel idiom of
creating an abstract interface with a struct filled with function pointers.

the patch serie consist of very minor fixes followed by the core of the changes
to implement the new feature.

v2 changes:
- extract small changes from the core changes to ease minor fixes backport
- totally remove the io_napi_tracking_ops interface

Olivier Langlois (3):
  io_uring/napi: protect concurrent io_napi_entry timeout accesses
  io_uring/napi: fix io_napi_entry RCU accesses
  io_uring/napi: add static napi tracking strategy

 include/linux/io_uring_types.h |   2 +-
 include/uapi/linux/io_uring.h  |  32 +++++++-
 io_uring/fdinfo.c              |  36 +++++++++
 io_uring/napi.c                | 135 ++++++++++++++++++++++++++-------
 io_uring/napi.h                |  15 +++-
 5 files changed, 186 insertions(+), 34 deletions(-)

-- 
2.46.0

[PATCH v2 1/3] io_uring/napi: protect concurrent io_napi_entry timeout accesses

[Olivier Langlois]

io_napi_entry timeout value can be updated while accessed from the poll
functions.

Its concurrent accesses are wrapped with READ_ONCE()/WRITE_ONCE() macros
to avoid incorrect compiler optimizations.

Signed-off-by: Olivier Langlois <olivier@trillion01.com>
---
 io_uring/napi.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/io_uring/napi.c b/io_uring/napi.c
index 1de1d4d62925..1dd2df9da468 100644
--- a/io_uring/napi.c
+++ b/io_uring/napi.c
@@ -60,7 +60,7 @@ void __io_napi_add(struct io_ring_ctx *ctx, struct socket *sock)
 	rcu_read_lock();
 	e = io_napi_hash_find(hash_list, napi_id);
 	if (e) {
-		e->timeout = jiffies + NAPI_TIMEOUT;
+		WRITE_ONCE(e->timeout, jiffies + NAPI_TIMEOUT);
 		rcu_read_unlock();
 		return;
 	}
@@ -92,7 +92,7 @@ static void __io_napi_remove_stale(struct io_ring_ctx *ctx)
 
 	spin_lock(&ctx->napi_lock);
 	hash_for_each(ctx->napi_ht, i, e, node) {
-		if (time_after(jiffies, e->timeout)) {
+		if (time_after(jiffies, READ_ONCE(e->timeout))) {
 			list_del(&e->list);
 			hash_del_rcu(&e->node);
 			kfree_rcu(e, rcu);
@@ -150,7 +150,7 @@ static bool __io_napi_do_busy_loop(struct io_ring_ctx *ctx,
 		napi_busy_loop_rcu(e->napi_id, loop_end, loop_end_arg,
 				   ctx->napi_prefer_busy_poll, BUSY_POLL_BUDGET);
 
-		if (time_after(jiffies, e->timeout))
+		if (time_after(jiffies, READ_ONCE(e->timeout)))
 			is_stale = true;
 	}
 
-- 
2.46.0

[PATCH v2 2/3] io_uring/napi: fix io_napi_entry RCU accesses

[Olivier Langlois]

correct 3 RCU structures modifications that were not using the RCU
functions to make their update.

Signed-off-by: Olivier Langlois <olivier@trillion01.com>
---
 io_uring/napi.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/io_uring/napi.c b/io_uring/napi.c
index 1dd2df9da468..738d88bc050a 100644
--- a/io_uring/napi.c
+++ b/io_uring/napi.c
@@ -81,7 +81,7 @@ void __io_napi_add(struct io_ring_ctx *ctx, struct socket *sock)
 	}
 
 	hlist_add_tail_rcu(&e->node, hash_list);
-	list_add_tail(&e->list, &ctx->napi_list);
+	list_add_tail_rcu(&e->list, &ctx->napi_list);
 	spin_unlock(&ctx->napi_lock);
 }
 
@@ -91,9 +91,15 @@ static void __io_napi_remove_stale(struct io_ring_ctx *ctx)
 	unsigned int i;
 
 	spin_lock(&ctx->napi_lock);
+	/*
+	 * hash_for_each_safe() is not required as long as:
+	 * 1. hash_del_rcu() does not reset the deleted node next pointer
+	 * 2. kfree_rcu() delays the memory freeing until the next quiescent
+	 *    state
+	 */
 	hash_for_each(ctx->napi_ht, i, e, node) {
 		if (time_after(jiffies, READ_ONCE(e->timeout))) {
-			list_del(&e->list);
+			list_del_rcu(&e->list);
 			hash_del_rcu(&e->node);
 			kfree_rcu(e, rcu);
 		}
@@ -207,6 +213,7 @@ void io_napi_free(struct io_ring_ctx *ctx)
 	unsigned int i;
 
 	spin_lock(&ctx->napi_lock);
+	INIT_LIST_HEAD_RCU(&ctx->napi_list);
 	hash_for_each(ctx->napi_ht, i, e, node) {
 		hash_del_rcu(&e->node);
 		kfree_rcu(e, rcu);
-- 
2.46.0

[PATCH v2 3/3] io_uring/napi: add static napi tracking strategy

[Olivier Langlois]

add the static napi tracking strategy that allows the user to manually
manage the napi ids list to busy poll and offload the ring from
dynamically update the list.

Signed-off-by: Olivier Langlois <olivier@trillion01.com>
---
 include/linux/io_uring_types.h |   2 +-
 include/uapi/linux/io_uring.h  |  32 ++++++++-
 io_uring/fdinfo.c              |  36 ++++++++++
 io_uring/napi.c                | 118 +++++++++++++++++++++++++++------
 io_uring/napi.h                |  15 +++--
 5 files changed, 174 insertions(+), 29 deletions(-)

diff --git a/include/linux/io_uring_types.h b/include/linux/io_uring_types.h
index 3315005df117..f0a0cb2518bb 100644
--- a/include/linux/io_uring_types.h
+++ b/include/linux/io_uring_types.h
@@ -406,7 +406,7 @@ struct io_ring_ctx {
 	/* napi busy poll default timeout */
 	ktime_t			napi_busy_poll_dt;
 	bool			napi_prefer_busy_poll;
-	bool			napi_enabled;
+	u8			napi_track_mode;
 
 	DECLARE_HASHTABLE(napi_ht, 4);
 #endif
diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index adc2524fd8e3..10d9030c4242 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -728,12 +728,40 @@ struct io_uring_buf_status {
 	__u32	resv[8];
 };
 
+enum io_uring_napi_op {
+	/* register/ungister backward compatible opcode */
+	IO_URING_NAPI_REGISTER_OP = 0,
+
+	/* opcodes to update napi_list when static tracking is used */
+	IO_URING_NAPI_STATIC_ADD_ID = 1,
+	IO_URING_NAPI_STATIC_DEL_ID = 2
+};
+
+enum io_uring_napi_tracking_strategy {
+	/* value must be 0 for backward compatibility */
+	IO_URING_NAPI_TRACKING_DYNAMIC = 0,
+	IO_URING_NAPI_TRACKING_STATIC = 1,
+	IO_URING_NAPI_TRACKING_INACTIVE = 255
+};
+
 /* argument for IORING_(UN)REGISTER_NAPI */
 struct io_uring_napi {
 	__u32	busy_poll_to;
 	__u8	prefer_busy_poll;
-	__u8	pad[3];
-	__u64	resv;
+
+	/* a io_uring_napi_op value */
+	__u8	opcode;
+	__u8	pad[2];
+
+	/*
+	 * for IO_URING_NAPI_REGISTER_OP, it is a
+	 * io_uring_napi_tracking_strategy value.
+	 *
+	 * for IO_URING_NAPI_STATIC_ADD_ID/IO_URING_NAPI_STATIC_DEL_ID
+	 * it is the napi id to add/del from napi_list.
+	 */
+	__u32	op_param;
+	__u32	resv;
 };
 
 /*
diff --git a/io_uring/fdinfo.c b/io_uring/fdinfo.c
index b1e0e0d85349..595a066ba250 100644
--- a/io_uring/fdinfo.c
+++ b/io_uring/fdinfo.c
@@ -46,6 +46,41 @@ static __cold int io_uring_show_cred(struct seq_file *m, unsigned int id,
 	return 0;
 }
 
+#ifdef CONFIG_NET_RX_BUSY_POLL
+static void common_tracking_show_fdinfo(struct io_ring_ctx *ctx,
+					struct seq_file *m,
+					const char *tracking_strategy)
+{
+	seq_puts(m, "NAPI:\tenabled\n");
+	seq_printf(m, "napi tracking:\t%s\n", tracking_strategy);
+	seq_printf(m, "napi_busy_poll_dt:\t%llu\n", ctx->napi_busy_poll_dt);
+	if (ctx->napi_prefer_busy_poll)
+		seq_puts(m, "napi_prefer_busy_poll:\ttrue\n");
+	else
+		seq_puts(m, "napi_prefer_busy_poll:\tfalse\n");
+}
+
+static void napi_show_fdinfo(struct io_ring_ctx *ctx, struct seq_file *m)
+{
+	switch (READ_ONCE(ctx->napi_track_mode)) {
+	case IO_URING_NAPI_TRACKING_INACTIVE:
+		seq_puts(m, "NAPI:\tdisabled\n");
+		break;
+	case IO_URING_NAPI_TRACKING_DYNAMIC:
+		common_tracking_show_fdinfo(ctx, m, "dynamic");
+		break;
+	case IO_URING_NAPI_TRACKING_STATIC:
+		common_tracking_show_fdinfo(ctx, m, "static");
+		break;
+	}
+}
+#else
+static inline void napi_show_fdinfo(struct io_ring_ctx *ctx,
+				    struct seq_file *m)
+{
+}
+#endif
+
 /*
  * Caller holds a reference to the file already, we don't need to do
  * anything else to get an extra reference.
@@ -223,5 +258,6 @@ __cold void io_uring_show_fdinfo(struct seq_file *m, struct file *file)
 	}
 
 	spin_unlock(&ctx->completion_lock);
+	napi_show_fdinfo(ctx, m);
 }
 #endif
diff --git a/io_uring/napi.c b/io_uring/napi.c
index 738d88bc050a..19dcb152dd31 100644
--- a/io_uring/napi.c
+++ b/io_uring/napi.c
@@ -38,22 +38,14 @@ static inline ktime_t net_to_ktime(unsigned long t)
 	return ns_to_ktime(t << 10);
 }
 
-void __io_napi_add(struct io_ring_ctx *ctx, struct socket *sock)
+int __io_napi_add_id(struct io_ring_ctx *ctx, unsigned int napi_id)
 {
 	struct hlist_head *hash_list;
-	unsigned int napi_id;
-	struct sock *sk;
 	struct io_napi_entry *e;
 
-	sk = sock->sk;
-	if (!sk)
-		return;
-
-	napi_id = READ_ONCE(sk->sk_napi_id);
-
 	/* Non-NAPI IDs can be rejected. */
 	if (napi_id < MIN_NAPI_ID)
-		return;
+		return -EINVAL;
 
 	hash_list = &ctx->napi_ht[hash_min(napi_id, HASH_BITS(ctx->napi_ht))];
 
@@ -62,13 +54,13 @@ void __io_napi_add(struct io_ring_ctx *ctx, struct socket *sock)
 	if (e) {
 		WRITE_ONCE(e->timeout, jiffies + NAPI_TIMEOUT);
 		rcu_read_unlock();
-		return;
+		return -EEXIST;
 	}
 	rcu_read_unlock();
 
 	e = kmalloc(sizeof(*e), GFP_NOWAIT);
 	if (!e)
-		return;
+		return -ENOMEM;
 
 	e->napi_id = napi_id;
 	e->timeout = jiffies + NAPI_TIMEOUT;
@@ -77,12 +69,37 @@ void __io_napi_add(struct io_ring_ctx *ctx, struct socket *sock)
 	if (unlikely(io_napi_hash_find(hash_list, napi_id))) {
 		spin_unlock(&ctx->napi_lock);
 		kfree(e);
-		return;
+		return -EEXIST;
 	}
 
 	hlist_add_tail_rcu(&e->node, hash_list);
 	list_add_tail_rcu(&e->list, &ctx->napi_list);
 	spin_unlock(&ctx->napi_lock);
+	return 0;
+}
+
+static int __io_napi_del_id(struct io_ring_ctx *ctx, unsigned int napi_id)
+{
+	struct hlist_head *hash_list;
+	struct io_napi_entry *e;
+
+	/* Non-NAPI IDs can be rejected. */
+	if (napi_id < MIN_NAPI_ID)
+		return -EINVAL;
+
+	hash_list = &ctx->napi_ht[hash_min(napi_id, HASH_BITS(ctx->napi_ht))];
+	spin_lock(&ctx->napi_lock);
+	e = io_napi_hash_find(hash_list, napi_id);
+	if (unlikely(!e)) {
+		spin_unlock(&ctx->napi_lock);
+		return -ENOENT;
+	}
+
+	list_del_rcu(&e->list);
+	hash_del_rcu(&e->node);
+	kfree_rcu(e, rcu);
+	spin_unlock(&ctx->napi_lock);
+	return 0;
 }
 
 static void __io_napi_remove_stale(struct io_ring_ctx *ctx)
@@ -142,8 +159,26 @@ static bool io_napi_busy_loop_should_end(void *data,
 	return false;
 }
 
-static bool __io_napi_do_busy_loop(struct io_ring_ctx *ctx,
-				   void *loop_end_arg)
+/*
+ * never report stale entries
+ */
+static bool static_tracking_do_busy_loop(struct io_ring_ctx *ctx,
+					 void *loop_end_arg)
+{
+	struct io_napi_entry *e;
+	bool (*loop_end)(void *, unsigned long) = NULL;
+
+	if (loop_end_arg)
+		loop_end = io_napi_busy_loop_should_end;
+
+	list_for_each_entry_rcu(e, &ctx->napi_list, list)
+		napi_busy_loop_rcu(e->napi_id, loop_end, loop_end_arg,
+				   ctx->napi_prefer_busy_poll, BUSY_POLL_BUDGET);
+	return false;
+}
+
+static bool dynamic_tracking_do_busy_loop(struct io_ring_ctx *ctx,
+					  void *loop_end_arg)
 {
 	struct io_napi_entry *e;
 	bool (*loop_end)(void *, unsigned long) = NULL;
@@ -163,6 +198,15 @@ static bool __io_napi_do_busy_loop(struct io_ring_ctx *ctx,
 	return is_stale;
 }
 
+static inline bool __io_napi_do_busy_loop(struct io_ring_ctx *ctx,
+					  void *loop_end_arg)
+{
+	if (READ_ONCE(ctx->napi_track_mode) == IO_URING_NAPI_TRACKING_STATIC)
+		return static_tracking_do_busy_loop(ctx, loop_end_arg);
+	else
+		return dynamic_tracking_do_busy_loop(ctx, loop_end_arg);
+}
+
 static void io_napi_blocking_busy_loop(struct io_ring_ctx *ctx,
 				       struct io_wait_queue *iowq)
 {
@@ -199,6 +243,7 @@ void io_napi_init(struct io_ring_ctx *ctx)
 	spin_lock_init(&ctx->napi_lock);
 	ctx->napi_prefer_busy_poll = false;
 	ctx->napi_busy_poll_dt = ns_to_ktime(sys_dt);
+	ctx->napi_track_mode = IO_URING_NAPI_TRACKING_INACTIVE;
 }
 
 /*
@@ -221,6 +266,24 @@ void io_napi_free(struct io_ring_ctx *ctx)
 	spin_unlock(&ctx->napi_lock);
 }
 
+static int io_napi_register_napi(struct io_ring_ctx *ctx,
+				 struct io_uring_napi *napi)
+{
+	switch (napi->op_param) {
+	case IO_URING_NAPI_TRACKING_DYNAMIC:
+	case IO_URING_NAPI_TRACKING_STATIC:
+		break;
+	default:
+		return -EINVAL;
+	}
+	/* clean the napi list for new settings */
+	io_napi_free(ctx);
+	WRITE_ONCE(ctx->napi_track_mode, napi->op_param);
+	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);
+	return 0;
+}
+
 /*
  * io_napi_register() - Register napi with io-uring
  * @ctx: pointer to io-uring context structure
@@ -232,7 +295,8 @@ int io_register_napi(struct io_ring_ctx *ctx, void __user *arg)
 {
 	const struct io_uring_napi curr = {
 		.busy_poll_to 	  = ktime_to_us(ctx->napi_busy_poll_dt),
-		.prefer_busy_poll = ctx->napi_prefer_busy_poll
+		.prefer_busy_poll = ctx->napi_prefer_busy_poll,
+		.op_param	  = ctx->napi_track_mode
 	};
 	struct io_uring_napi napi;
 
@@ -240,16 +304,26 @@ int io_register_napi(struct io_ring_ctx *ctx, void __user *arg)
 		return -EINVAL;
 	if (copy_from_user(&napi, arg, sizeof(napi)))
 		return -EFAULT;
-	if (napi.pad[0] || napi.pad[1] || napi.pad[2] || napi.resv)
+	if (napi.pad[0] || napi.pad[1] || napi.resv)
 		return -EINVAL;
 
 	if (copy_to_user(arg, &curr, sizeof(curr)))
 		return -EFAULT;
 
-	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;
+	switch (napi.opcode) {
+	case IO_URING_NAPI_REGISTER_OP:
+		return io_napi_register_napi(ctx, &napi);
+	case IO_URING_NAPI_STATIC_ADD_ID:
+		if (curr.op_param != IO_URING_NAPI_TRACKING_STATIC)
+			return -EINVAL;
+		return __io_napi_add_id(ctx, napi.op_param);
+	case IO_URING_NAPI_STATIC_DEL_ID:
+		if (curr.op_param != IO_URING_NAPI_TRACKING_STATIC)
+			return -EINVAL;
+		return __io_napi_del_id(ctx, napi.op_param);
+	default:
+		return -EINVAL;
+	}
 }
 
 /*
@@ -272,7 +346,7 @@ int io_unregister_napi(struct io_ring_ctx *ctx, void __user *arg)
 
 	WRITE_ONCE(ctx->napi_busy_poll_dt, 0);
 	WRITE_ONCE(ctx->napi_prefer_busy_poll, false);
-	WRITE_ONCE(ctx->napi_enabled, false);
+	WRITE_ONCE(ctx->napi_track_mode, IO_URING_NAPI_TRACKING_INACTIVE);
 	return 0;
 }
 
diff --git a/io_uring/napi.h b/io_uring/napi.h
index 27b88c3eb428..220574522484 100644
--- a/io_uring/napi.h
+++ b/io_uring/napi.h
@@ -15,7 +15,7 @@ void io_napi_free(struct io_ring_ctx *ctx);
 int io_register_napi(struct io_ring_ctx *ctx, void __user *arg);
 int io_unregister_napi(struct io_ring_ctx *ctx, void __user *arg);
 
-void __io_napi_add(struct io_ring_ctx *ctx, struct socket *sock);
+int __io_napi_add_id(struct io_ring_ctx *ctx, unsigned int napi_id);
 
 void __io_napi_adjust_timeout(struct io_ring_ctx *ctx,
 		struct io_wait_queue *iowq, ktime_t to_wait);
@@ -54,13 +54,20 @@ static inline void io_napi_add(struct io_kiocb *req)
 {
 	struct io_ring_ctx *ctx = req->ctx;
 	struct socket *sock;
+	struct sock *sk;
 
-	if (!READ_ONCE(ctx->napi_enabled))
+	if (READ_ONCE(ctx->napi_track_mode) != IO_URING_NAPI_TRACKING_DYNAMIC)
 		return;
 
 	sock = sock_from_file(req->file);
-	if (sock)
-		__io_napi_add(ctx, sock);
+	if (!sock)
+		return;
+
+	sk = sock->sk;
+	if (!sk)
+		return;
+
+	__io_napi_add_id(ctx, READ_ONCE(sk->sk_napi_id));
 }
 
 #else
-- 
2.46.0

Re: [PATCH v2 3/3] io_uring/napi: add static napi tracking strategy

[Jens Axboe]

On 9/16/24 1:20 PM, Olivier Langlois wrote:
> add the static napi tracking strategy that allows the user to manually
> manage the napi ids list to busy poll and offload the ring from
> dynamically update the list.

I like this, I suspect for many cases this is all you will need rather
than try and dynamically track multiple instances.

Away for the next week or so, so won't have time to do a proper review
until I'm back. Timing wise this doesn't matter too much as the 6.12
merge window is currently open, hence we cannot target this to anything
sooner than 6.13. So we have time to get this reviewed and queued up.

A few minor comments below.

> diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
> index adc2524fd8e3..10d9030c4242 100644
> --- a/include/uapi/linux/io_uring.h
> +++ b/include/uapi/linux/io_uring.h
> @@ -728,12 +728,40 @@ struct io_uring_buf_status {
>  	__u32	resv[8];
>  };
>  
> +enum io_uring_napi_op {
> +	/* register/ungister backward compatible opcode */
> +	IO_URING_NAPI_REGISTER_OP = 0,
> +
> +	/* opcodes to update napi_list when static tracking is used */
> +	IO_URING_NAPI_STATIC_ADD_ID = 1,
> +	IO_URING_NAPI_STATIC_DEL_ID = 2
> +};
> +
> +enum io_uring_napi_tracking_strategy {
> +	/* value must be 0 for backward compatibility */
> +	IO_URING_NAPI_TRACKING_DYNAMIC = 0,
> +	IO_URING_NAPI_TRACKING_STATIC = 1,
> +	IO_URING_NAPI_TRACKING_INACTIVE = 255
> +};

I think this is a fine way to do it, retaining compatability with what
we have now on the registration side.

>  /* argument for IORING_(UN)REGISTER_NAPI */
>  struct io_uring_napi {
>  	__u32	busy_poll_to;
>  	__u8	prefer_busy_poll;
> -	__u8	pad[3];
> -	__u64	resv;
> +
> +	/* a io_uring_napi_op value */
> +	__u8	opcode;
> +	__u8	pad[2];
> +
> +	/*
> +	 * for IO_URING_NAPI_REGISTER_OP, it is a
> +	 * io_uring_napi_tracking_strategy value.
> +	 *
> +	 * for IO_URING_NAPI_STATIC_ADD_ID/IO_URING_NAPI_STATIC_DEL_ID
> +	 * it is the napi id to add/del from napi_list.
> +	 */
> +	__u32	op_param;
> +	__u32	resv;
>  };

Looks good too.

> +static void common_tracking_show_fdinfo(struct io_ring_ctx *ctx,
> +					struct seq_file *m,
> +					const char *tracking_strategy)
> +{
> +	seq_puts(m, "NAPI:\tenabled\n");
> +	seq_printf(m, "napi tracking:\t%s\n", tracking_strategy);
> +	seq_printf(m, "napi_busy_poll_dt:\t%llu\n", ctx->napi_busy_poll_dt);
> +	if (ctx->napi_prefer_busy_poll)
> +		seq_puts(m, "napi_prefer_busy_poll:\ttrue\n");
> +	else
> +		seq_puts(m, "napi_prefer_busy_poll:\tfalse\n");
> +}
> +
> +static void napi_show_fdinfo(struct io_ring_ctx *ctx, struct seq_file *m)
> +{
> +	switch (READ_ONCE(ctx->napi_track_mode)) {
> +	case IO_URING_NAPI_TRACKING_INACTIVE:
> +		seq_puts(m, "NAPI:\tdisabled\n");
> +		break;
> +	case IO_URING_NAPI_TRACKING_DYNAMIC:
> +		common_tracking_show_fdinfo(ctx, m, "dynamic");
> +		break;
> +	case IO_URING_NAPI_TRACKING_STATIC:
> +		common_tracking_show_fdinfo(ctx, m, "static");
> +		break;
> +	}
> +}

Maybe add an "unknown" default entry here, just in case it ever changes
and someone forgets to update the fdinfo code.

> +static inline bool __io_napi_do_busy_loop(struct io_ring_ctx *ctx,
> +					  void *loop_end_arg)
> +{
> +	if (READ_ONCE(ctx->napi_track_mode) == IO_URING_NAPI_TRACKING_STATIC)
> +		return static_tracking_do_busy_loop(ctx, loop_end_arg);
> +	else
> +		return dynamic_tracking_do_busy_loop(ctx, loop_end_arg);
> +}
> +

Minor style nit:

	if (READ_ONCE(ctx->napi_track_mode) == IO_URING_NAPI_TRACKING_STATIC)
		return static_tracking_do_busy_loop(ctx, loop_end_arg);
	return dynamic_tracking_do_busy_loop(ctx, loop_end_arg);

would do.

-- 
Jens Axboe

Re: [PATCH v2 3/3] io_uring/napi: add static napi tracking strategy

[Olivier Langlois]

On Mon, 2024-09-16 at 21:09 -0600, Jens Axboe wrote:
> On 9/16/24 1:20 PM, Olivier Langlois wrote:
> > 
> > +static void napi_show_fdinfo(struct io_ring_ctx *ctx, struct
> > seq_file *m)
> > +{
> > +	switch (READ_ONCE(ctx->napi_track_mode)) {
> > +	case IO_URING_NAPI_TRACKING_INACTIVE:
> > +		seq_puts(m, "NAPI:\tdisabled\n");
> > +		break;
> > +	case IO_URING_NAPI_TRACKING_DYNAMIC:
> > +		common_tracking_show_fdinfo(ctx, m, "dynamic");
> > +		break;
> > +	case IO_URING_NAPI_TRACKING_STATIC:
> > +		common_tracking_show_fdinfo(ctx, m, "static");
> > +		break;
> > +	}
> > +}
> 
> Maybe add an "unknown" default entry here, just in case it ever
> changes
> and someone forgets to update the fdinfo code.

ok
> 
> > +static inline bool __io_napi_do_busy_loop(struct io_ring_ctx *ctx,
> > +					  void *loop_end_arg)
> > +{
> > +	if (READ_ONCE(ctx->napi_track_mode) ==
> > IO_URING_NAPI_TRACKING_STATIC)
> > +		return static_tracking_do_busy_loop(ctx,
> > loop_end_arg);
> > +	else
> > +		return dynamic_tracking_do_busy_loop(ctx,
> > loop_end_arg);
> > +}
> > +
> 
> Minor style nit:
> 
> 	if (READ_ONCE(ctx->napi_track_mode) ==
> IO_URING_NAPI_TRACKING_STATIC)
> 		return static_tracking_do_busy_loop(ctx,
> loop_end_arg);
> 	return dynamic_tracking_do_busy_loop(ctx, loop_end_arg);
> 
> would do.
> 
will do.

Also, after looking at Pavel work at

https://github.com/isilence/linux/commits/manual-napi/

I have found a way to improve patch #2 of this serie...

v3 is going to be sweet!