• liubo's avatar
    Btrfs: add initial tracepoint support for btrfs · 1abe9b8a
    liubo authored
    Tracepoints can provide insight into why btrfs hits bugs and be greatly
    helpful for debugging, e.g
                  dd-7822  [000]  2121.641088: btrfs_inode_request: root = 5(FS_TREE), gen = 4, ino = 256, blocks = 8, disk_i_size = 0, last_trans = 8, logged_trans = 0
                  dd-7822  [000]  2121.641100: btrfs_inode_new: root = 5(FS_TREE), gen = 8, ino = 257, blocks = 0, disk_i_size = 0, last_trans = 0, logged_trans = 0
     btrfs-transacti-7804  [001]  2146.935420: btrfs_cow_block: root = 2(EXTENT_TREE), refs = 2, orig_buf = 29368320 (orig_level = 0), cow_buf = 29388800 (cow_level = 0)
     btrfs-transacti-7804  [001]  2146.935473: btrfs_cow_block: root = 1(ROOT_TREE), refs = 2, orig_buf = 29364224 (orig_level = 0), cow_buf = 29392896 (cow_level = 0)
     btrfs-transacti-7804  [001]  2146.972221: btrfs_transaction_commit: root = 1(ROOT_TREE), gen = 8
       flush-btrfs-2-7821  [001]  2155.824210: btrfs_chunk_alloc: root = 3(CHUNK_TREE), offset = 1103101952, size = 1073741824, num_stripes = 1, sub_stripes = 0, type = DATA
       flush-btrfs-2-7821  [001]  2155.824241: btrfs_cow_block: root = 2(EXTENT_TREE), refs = 2, orig_buf = 29388800 (orig_level = 0), cow_buf = 29396992 (cow_level = 0)
       flush-btrfs-2-7821  [001]  2155.824255: btrfs_cow_block: root = 4(DEV_TREE), refs = 2, orig_buf = 29372416 (orig_level = 0), cow_buf = 29401088 (cow_level = 0)
       flush-btrfs-2-7821  [000]  2155.824329: btrfs_cow_block: root = 3(CHUNK_TREE), refs = 2, orig_buf = 20971520 (orig_level = 0), cow_buf = 20975616 (cow_level = 0)
     btrfs-endio-wri-7800  [001]  2155.898019: btrfs_cow_block: root = 5(FS_TREE), refs = 2, orig_buf = 29384704 (orig_level = 0), cow_buf = 29405184 (cow_level = 0)
     btrfs-endio-wri-7800  [001]  2155.898043: btrfs_cow_block: root = 7(CSUM_TREE), refs = 2, orig_buf = 29376512 (orig_level = 0), cow_buf = 29409280 (cow_level = 0)
    
    Here is what I have added:
    
    1) ordere_extent:
            btrfs_ordered_extent_add
            btrfs_ordered_extent_remove
            btrfs_ordered_extent_start
            btrfs_ordered_extent_put
    
    These provide critical information to understand how ordered_extents are
    updated.
    
    2) extent_map:
            btrfs_get_extent
    
    extent_map is used in both read and write cases, and it is useful for tracking
    how btrfs specific IO is running.
    
    3) writepage:
            __extent_writepage
            btrfs_writepage_end_io_hook
    
    Pages are cirtical resourses and produce a lot of corner cases during writeback,
    so it is valuable to know how page is written to disk.
    
    4) inode:
            btrfs_inode_new
            btrfs_inode_request
            btrfs_inode_evict
    
    These can show where and when a inode is created, when a inode is evicted.
    
    5) sync:
            btrfs_sync_file
            btrfs_sync_fs
    
    These show sync arguments.
    
    6) transaction:
            btrfs_transaction_commit
    
    In transaction based filesystem, it will be useful to know the generation and
    who does commit.
    
    7) back reference and cow:
    	btrfs_delayed_tree_ref
    	btrfs_delayed_data_ref
    	btrfs_delayed_ref_head
    	btrfs_cow_block
    
    Btrfs natively supports back references, these tracepoints are helpful on
    understanding btrfs's COW mechanism.
    
    8) chunk:
    	btrfs_chunk_alloc
    	btrfs_chunk_free
    
    Chunk is a link between physical offset and logical offset, and stands for space
    infomation in btrfs, and these are helpful on tracing space things.
    
    9) reserved_extent:
    	btrfs_reserved_extent_alloc
    	btrfs_reserved_extent_free
    
    These can show how btrfs uses its space.
    Signed-off-by: default avatarLiu Bo <liubo2009@cn.fujitsu.com>
    Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
    1abe9b8a
ctree.h 84 KB