Commit ac1ea10e authored by Josef Bacik's avatar Josef Bacik Committed by David Sterba
Browse files

btrfs: add a trace point for reserve tickets 



While debugging a ENOSPC related performance problem I needed to see the
time difference between start and end of a reserve ticket, so add a
trace point to report when we handle a reserve ticket.

I opted to spit out start_ns itself without calculating the difference
because there could be a gap between enabling the tracepoint and setting
start_ns.  Doing it this way allows us to filter on 0 start_ns so we
don't get bogus entries, and we can easily calculate the time difference
with bpftrace or something else.

Reviewed-by: default avatarNikolay Borisov <nborisov@suse.com>
Signed-off-by: default avatarJosef Bacik <josef@toxicpanda.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 91e79a83

fs/btrfs/space-info.c

+11 −1
Original line number Diff line number Diff line
@@ -1220,6 +1220,8 @@ static void wait_reserve_ticket(struct btrfs_fs_info *fs_info, 
 * @fs_info:    the filesystem

 * @space_info: space info for the reservation

 * @ticket:     ticket for the reservation

 * @start_ns:   timestamp when the reservation started

 * @orig_bytes: amount of bytes originally reserved

 * @flush:      how much we can flush

 *

 * This does the work of figuring out how to flush for the ticket, waiting for
@@ -1228,6 +1230,7 @@ static void wait_reserve_ticket(struct btrfs_fs_info *fs_info, 
static int handle_reserve_ticket(struct btrfs_fs_info *fs_info,

				 struct btrfs_space_info *space_info,

				 struct reserve_ticket *ticket,

				 u64 start_ns, u64 orig_bytes,

				 enum btrfs_reserve_flush_enum flush)

{

	int ret;
@@ -1283,6 +1286,8 @@ static int handle_reserve_ticket(struct btrfs_fs_info *fs_info, 
	 * space wasn't reserved at all).

	 */

	ASSERT(!(ticket->bytes == 0 && ticket->error));

	trace_btrfs_reserve_ticket(fs_info, space_info->flags, orig_bytes,

				   start_ns, flush, ticket->error);

	return ret;

}
@@ -1317,6 +1322,7 @@ static int __reserve_bytes(struct btrfs_fs_info *fs_info, 
{

	struct work_struct *async_work;

	struct reserve_ticket ticket;

	u64 start_ns = 0;

	u64 used;

	int ret = 0;

	bool pending_tickets;
@@ -1369,6 +1375,9 @@ static int __reserve_bytes(struct btrfs_fs_info *fs_info, 
		space_info->reclaim_size += ticket.bytes;

		init_waitqueue_head(&ticket.wait);

		ticket.steal = (flush == BTRFS_RESERVE_FLUSH_ALL_STEAL);

		if (trace_btrfs_reserve_ticket_enabled())

			start_ns = ktime_get_ns();



		if (flush == BTRFS_RESERVE_FLUSH_ALL ||

		    flush == BTRFS_RESERVE_FLUSH_ALL_STEAL ||

		    flush == BTRFS_RESERVE_FLUSH_DATA) {
@@ -1405,7 +1414,8 @@ static int __reserve_bytes(struct btrfs_fs_info *fs_info, 
	if (!ret || flush == BTRFS_RESERVE_NO_FLUSH)

		return ret;



	return handle_reserve_ticket(fs_info, space_info, &ticket, flush);

	return handle_reserve_ticket(fs_info, space_info, &ticket, start_ns,

				     orig_bytes, flush);

}



/**

include/trace/events/btrfs.h

+29 −0
Original line number Diff line number Diff line
@@ -2026,6 +2026,35 @@ TRACE_EVENT(btrfs_convert_extent_bit, 
		  __print_flags(__entry->clear_bits, "|", EXTENT_FLAGS))

);



TRACE_EVENT(btrfs_reserve_ticket,

	TP_PROTO(const struct btrfs_fs_info *fs_info, u64 flags, u64 bytes,

		 u64 start_ns, int flush, int error),



	TP_ARGS(fs_info, flags, bytes, start_ns, flush, error),



	TP_STRUCT__entry_btrfs(

		__field(	u64,	flags		)

		__field(	u64,	bytes		)

		__field(	u64,	start_ns	)

		__field(	int,	flush		)

		__field(	int,	error		)

	),



	TP_fast_assign_btrfs(fs_info,

		__entry->flags		= flags;

		__entry->bytes		= bytes;

		__entry->start_ns	= start_ns;

		__entry->flush		= flush;

		__entry->error		= error;

	),



	TP_printk_btrfs("flags=%s bytes=%llu start_ns=%llu flush=%s error=%d",

			__print_flags(__entry->flags, "|", BTRFS_GROUP_FLAGS),

			__entry->bytes, __entry->start_ns,

			__print_symbolic(__entry->flush, FLUSH_ACTIONS),

			__entry->error)

);



DECLARE_EVENT_CLASS(btrfs_sleep_tree_lock,

	TP_PROTO(const struct extent_buffer *eb, u64 start_ns),