diff mbox

[2/2] blk-mq-debugfs: add q->mq_freeze_depth output

Message ID d4ab26006c6b454db94d548df10da3ce8908c8a1.1488393750.git.osandov@fb.com (mailing list archive)
State New, archived
Headers show

Commit Message

Omar Sandoval March 1, 2017, 6:42 p.m. UTC 
From: Omar Sandoval <osandov@fb.com>

This can be used to diagnose freeze-related hangs.

Signed-off-by: Omar Sandoval <osandov@fb.com>
---
 block/blk-mq-debugfs.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

Comments

Jens Axboe March 2, 2017, 2:25 a.m. UTC | #1 
On 03/01/2017 11:42 AM, Omar Sandoval wrote:
> From: Omar Sandoval <osandov@fb.com>
> 
> This can be used to diagnose freeze-related hangs.

Do we really need this? For the loop case, it was painfully
obvious that it was a count issue. And I can't think of any
cases where it would have helped us, outside of rewriting
core parts (like the first edition of the shadow requests
for the scheduler).

Not strongly opposed to it, feel free to convince me.
Omar Sandoval March 2, 2017, 3:07 a.m. UTC | #2 
On Wed, Mar 01, 2017 at 07:25:59PM -0700, Jens Axboe wrote:
> On 03/01/2017 11:42 AM, Omar Sandoval wrote:
> > From: Omar Sandoval <osandov@fb.com>
> > 
> > This can be used to diagnose freeze-related hangs.
> 
> Do we really need this? For the loop case, it was painfully
> obvious that it was a count issue. And I can't think of any
> cases where it would have helped us, outside of rewriting
> core parts (like the first edition of the shadow requests
> for the scheduler).
> 
> Not strongly opposed to it, feel free to convince me.

I don't feel a burning need for it, let's just drop it.
diff mbox

Patch

diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
index f6d917977b33..1459546788da 100644
--- a/block/blk-mq-debugfs.c
+++ b/block/blk-mq-debugfs.c
@@ -29,6 +29,26 @@  struct blk_mq_debugfs_attr {
 	const struct file_operations *fops;
 };
 
+static int queue_freeze_depth_show(struct seq_file *m, void *v)
+{
+	struct request_queue *q = m->private;
+
+	seq_printf(m, "%d\n", atomic_read(&q->mq_freeze_depth));
+	return 0;
+}
+
+static int queue_freeze_depth_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, queue_freeze_depth_show, inode->i_private);
+}
+
+static const struct file_operations queue_freeze_depth_fops = {
+	.open		= queue_freeze_depth_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= single_release,
+};
+
 static int blk_mq_debugfs_seq_open(struct inode *inode, struct file *file,
 				   const struct seq_operations *ops)
 {
@@ -636,6 +656,11 @@  static const struct file_operations ctx_completed_fops = {
 	.release	= single_release,
 };
 
+static const struct blk_mq_debugfs_attr blk_mq_debugfs_queue_attrs[] = {
+	{"freeze_depth", 0400, &queue_freeze_depth_fops},
+	{},
+};
+
 static const struct blk_mq_debugfs_attr blk_mq_debugfs_hctx_attrs[] = {
 	{"state", 0400, &hctx_state_fops},
 	{"flags", 0400, &hctx_flags_fops},
@@ -753,6 +778,9 @@  int blk_mq_debugfs_register_hctxs(struct request_queue *q)
 	if (!q->mq_debugfs_dir)
 		goto err;
 
+	if (!debugfs_create_files(q->mq_debugfs_dir, q, blk_mq_debugfs_queue_attrs))
+		return -ENOMEM;
+
 	queue_for_each_hw_ctx(q, hctx, i) {
 		if (blk_mq_debugfs_register_hctx(q, hctx))
 			goto err;