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 tracpoint 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: Nikolay Borisov <[email protected]> Signed-off-by: Josef Bacik <[email protected]> --- fs/btrfs/space-info.c | 12 +++++++++++- include/trace/events/btrfs.h | 29 +++++++++++++++++++++++++++++ 2 files changed, 40 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/space-info.c b/fs/btrfs/space-info.c index 975bb109e8b9..af6ab30e36e7 100644 --- a/fs/btrfs/space-info.c +++ b/fs/btrfs/space-info.c @@ -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); } /** diff --git a/include/trace/events/btrfs.h b/include/trace/events/btrfs.h index b9896fc06160..b0ea2a108be3 100644 --- a/include/trace/events/btrfs.h +++ b/include/trace/events/btrfs.h @@ -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), -- 2.26.2
