Commit dbbe9c64 authored Sep 29, 2020 by Joseph Qi Committed by Jens Axboe Sep 30, 2020

io_uring: show sqthread pid and cpu in fdinfo



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>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
[axboe: fixed for new shared SQPOLL]
Signed-off-by: Jens Axboe <axboe@kernel.dk>

parent af9c1a44

fs/io_uring.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -9124,6 +9124,7 @@ static int io_uring_show_cred(int id, void p, void data)

		static void __io_uring_show_fdinfo(struct io_ring_ctx ctx, struct seq_file m)
		{
		struct io_sq_data *sq = NULL;
		bool has_lock;
		int i;

		@@ -9135,6 +9136,11 @@ static void __io_uring_show_fdinfo(struct io_ring_ctx ctx, struct seq_file m)
		*/
		has_lock = mutex_trylock(&ctx->uring_lock);

		if (has_lock && (ctx->flags & IORING_SETUP_SQPOLL))
		sq = ctx->sq_data;

		seq_printf(m, "SqThread:\t%d\n", sq ? task_pid_nr(sq->thread) : -1);
		seq_printf(m, "SqThreadCpu:\t%d\n", sq ? task_cpu(sq->thread) : -1);
		seq_printf(m, "UserFiles:\t%u\n", ctx->nr_user_files);
		for (i = 0; has_lock && i < ctx->nr_user_files; i++) {
		struct fixed_file_table *table;

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