netdev - Re: [PATCH v13 4/7] io-uring: add napi busy poll support

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Message-ID: <4b05488a-6a12-2f23-f490-79dcc2bc5d59@kernel.dk>
Date: Thu, 18 May 2023 19:26:47 -0600
From: Jens Axboe <axboe@...nel.dk>
To: Stefan Roesch <shr@...kernel.io>, io-uring@...r.kernel.org,
 kernel-team@...com
Cc: ammarfaizi2@...weeb.org, netdev@...r.kernel.org, kuba@...nel.org,
 olivier@...llion01.com
Subject: Re: [PATCH v13 4/7] io-uring: add napi busy poll support

On 5/18/23 3:17?PM, Stefan Roesch wrote:
> diff --git a/io_uring/poll.c b/io_uring/poll.c
> index c90e47dc1e29..0284849793bb 100644
> --- a/io_uring/poll.c
> +++ b/io_uring/poll.c
> @@ -15,6 +15,7 @@
>  
>  #include "io_uring.h"
>  #include "refs.h"
> +#include "napi.h"
>  #include "opdef.h"
>  #include "kbuf.h"
>  #include "poll.h"
> @@ -631,6 +632,7 @@ static int __io_arm_poll_handler(struct io_kiocb *req,
>  		__io_poll_execute(req, mask);
>  		return 0;
>  	}
> +	io_napi_add(req);
>  
>  	if (ipt->owning) {
>  		/*

One thing that bothers me a bit here is that we then do:

static inline void io_napi_add(struct io_kiocb *req)
{
	struct io_ring_ctx *ctx = req->ctx;

	if (!READ_ONCE(ctx->napi_busy_poll_to))
		return;

	__io_napi_add(ctx, req->file);
}

which will do __io_napi_add() for any file type, even though we really
just want sockets here. I initially thought we could add a fast flag for
the type (like we do for IS_REG), but I think we can just do this
incremental and call it good enough.

Unfortunately sock_from_file() is also a function call... But not a huge
problem.


diff --git a/io_uring/napi.c b/io_uring/napi.c
index 5790b2daf1d0..8ec016899539 100644
--- a/io_uring/napi.c
+++ b/io_uring/napi.c
@@ -33,18 +33,13 @@ static struct io_napi_entry *io_napi_hash_find(struct hlist_head *hash_list,
 	return NULL;
 }
 
-void __io_napi_add(struct io_ring_ctx *ctx, struct file *file)
+void __io_napi_add(struct io_ring_ctx *ctx, struct socket *sock)
 {
 	struct hlist_head *hash_list;
 	unsigned int napi_id;
-	struct socket *sock;
 	struct sock *sk;
 	struct io_napi_entry *e;
 
-	sock = sock_from_file(file);
-	if (!sock)
-		return;
-
 	sk = sock->sk;
 	if (!sk)
 		return;
diff --git a/io_uring/napi.h b/io_uring/napi.h
index 69c1970cbecc..08cee8f4c9d1 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 file *file);
+void __io_napi_add(struct io_ring_ctx *ctx, struct socket *sock);
 
 void __io_napi_adjust_timeout(struct io_ring_ctx *ctx,
 		struct io_wait_queue *iowq, struct timespec64 *ts);
@@ -53,46 +53,51 @@ static inline void io_napi_busy_loop(struct io_ring_ctx *ctx,
 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))
 		return;
 
-	__io_napi_add(ctx, req->file);
+	sock = sock_from_file(req->file);
+	if (sock)
+		__io_napi_add(ctx, sock);
 }
 

-- 
Jens Axboe