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io_uring: show sqthread pid and cpu in fdinfo

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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>
This commit is contained in:
Joseph Qi 2020-09-29 09:01:22 -06:00 committed by Jens Axboe
parent af9c1a44f8
commit dbbe9c6424
1 changed files with 6 additions and 0 deletions
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6
fs/io_uring.c
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@ -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;