[PATCH RESEND] io_uring: show sqthread pid and cpu in fdinfo

[PATCH RESEND] io_uring: show sqthread pid and cpu in fdinfo

[Joseph Qi]

In most cases we'll specify IORING_SETUP_SQPOLL and run multiple
io_uring instances in a host. Since all sqthreads are named
"io_uring-sq", it's hard to distinguish the relations between
application process and its io_uring sqthread.
With this patch, application can get its corresponding sqthread pid
and cpu through show_fdinfo.
Steps:
1. Get io_uring fd first.
$ ls -l /proc/<pid>/fd | grep -w io_uring
2. Then get io_uring instance related info, including corresponding
sqthread pid and cpu.
$ cat /proc/<pid>/fdinfo/<io_uring_fd>

pos:	0
flags:	02000002
mnt_id:	13
SqThread:	6929
SqThreadCpu:	2
UserFiles:	1
    0: testfile
UserBufs:	0
PollList:

Signed-off-by: Joseph Qi <joseph.qi@linux.alibaba.com>
---
 fs/io_uring.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 8b426aa..9c8b3b3 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -8415,6 +8415,10 @@ static void __io_uring_show_fdinfo(struct io_ring_ctx *ctx, struct seq_file *m)
 	int i;
 
 	mutex_lock(&ctx->uring_lock);
+	seq_printf(m, "SqThread:\t%d\n", (ctx->flags & IORING_SETUP_SQPOLL) ?
+					 task_pid_nr(ctx->sqo_thread) : -1);
+	seq_printf(m, "SqThreadCpu:\t%d\n", (ctx->flags & IORING_SETUP_SQPOLL) ?
+					    task_cpu(ctx->sqo_thread) : -1);
 	seq_printf(m, "UserFiles:\t%u\n", ctx->nr_user_files);
 	for (i = 0; i < ctx->nr_user_files; i++) {
 		struct fixed_file_table *table;
-- 
1.8.3.1

Re: [PATCH RESEND] io_uring: show sqthread pid and cpu in fdinfo

[Stefano Garzarella]

On Thu, Sep 24, 2020 at 10:55:24AM +0800, Joseph Qi wrote:
> In most cases we'll specify IORING_SETUP_SQPOLL and run multiple
> io_uring instances in a host. Since all sqthreads are named
> "io_uring-sq", it's hard to distinguish the relations between
> application process and its io_uring sqthread.
> With this patch, application can get its corresponding sqthread pid
> and cpu through show_fdinfo.
> Steps:
> 1. Get io_uring fd first.
> $ ls -l /proc/<pid>/fd | grep -w io_uring
> 2. Then get io_uring instance related info, including corresponding
> sqthread pid and cpu.
> $ cat /proc/<pid>/fdinfo/<io_uring_fd>
> 
> pos:	0
> flags:	02000002
> mnt_id:	13
> SqThread:	6929
> SqThreadCpu:	2
> UserFiles:	1
>     0: testfile
> UserBufs:	0
> PollList:
> 
> Signed-off-by: Joseph Qi <joseph.qi@linux.alibaba.com>
> ---
>  fs/io_uring.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index 8b426aa..9c8b3b3 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -8415,6 +8415,10 @@ static void __io_uring_show_fdinfo(struct io_ring_ctx *ctx, struct seq_file *m)
>  	int i;
>  
>  	mutex_lock(&ctx->uring_lock);
> +	seq_printf(m, "SqThread:\t%d\n", (ctx->flags & IORING_SETUP_SQPOLL) ?
> +					 task_pid_nr(ctx->sqo_thread) : -1);

What about 'SqThreadPID'?

> +	seq_printf(m, "SqThreadCpu:\t%d\n", (ctx->flags & IORING_SETUP_SQPOLL) ?
> +					    task_cpu(ctx->sqo_thread) : -1);
>  	seq_printf(m, "UserFiles:\t%u\n", ctx->nr_user_files);
>  	for (i = 0; i < ctx->nr_user_files; i++) {
>  		struct fixed_file_table *table;
> -- 
> 1.8.3.1
> 

With or without that changed, it looks good to me:

Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>

Thanks,
Stefano

Re: [PATCH RESEND] io_uring: show sqthread pid and cpu in fdinfo

[Jens Axboe]

On 9/23/20 8:55 PM, Joseph Qi wrote:
> In most cases we'll specify IORING_SETUP_SQPOLL and run multiple
> io_uring instances in a host. Since all sqthreads are named
> "io_uring-sq", it's hard to distinguish the relations between
> application process and its io_uring sqthread.
> With this patch, application can get its corresponding sqthread pid
> and cpu through show_fdinfo.
> Steps:
> 1. Get io_uring fd first.
> $ ls -l /proc/<pid>/fd | grep -w io_uring
> 2. Then get io_uring instance related info, including corresponding
> sqthread pid and cpu.
> $ cat /proc/<pid>/fdinfo/<io_uring_fd>

Applied, thanks.

-- 
Jens Axboe