On 5/22/24 10:57, Jens Axboe wrote:
On 5/22/24 11:38 AM, Bart Van Assche wrote:
On 5/22/24 00:48, Yunlong Xing wrote:
@@ -1913,6 +1921,10 @@ static void loop_handle_cmd(struct loop_cmd *cmd)
set_active_memcg(old_memcg);
css_put(cmd_memcg_css);
}
+
+ if (ori_ioprio != cmd_ioprio)
+ set_task_ioprio(current, ori_ioprio);
+
failed:
/* complete non-aio request */
if (!use_aio || ret) {
Does adding this call in the hot path have a measurable performance impact?
It's loop, I would not be concerned with overhead. But it does look pretty
bogus to modify the task ioprio from here.
Hi Jens,
Maybe Yunlong uses that call to pass the I/O priority to the I/O submitter?
I think that it is easy to pass the I/O priority to the kiocb submitted by
lo_rw_aio() without calling set_task_ioprio().
lo_read_simple() and lo_write_simple() however call vfs_iter_read() /
vfs_iter_write(). This results in a call of do_iter_readv_writev() and
init_sync_kiocb(). The latter function calls get_current_ioprio(). This is
probably why the set_task_ioprio() call has been added?
Thanks,
Bart.
