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Diffstat (limited to 'HOWTO/DTRACE.md')
| -rw-r--r-- | HOWTO/DTRACE.md | 343 |
1 files changed, 4 insertions, 339 deletions
diff --git a/HOWTO/DTRACE.md b/HOWTO/DTRACE.md index 90f4addefd..0c08b6cc3d 100644 --- a/HOWTO/DTRACE.md +++ b/HOWTO/DTRACE.md @@ -46,346 +46,11 @@ although it's considered experimental. The main development of the dtrace code still happens outside of Ericsson, but there is no need to fetch a patched version of the OTP source to get the basic funtionality. -Implementation summary ----------------------- +DTrace probe specifications +--------------------------- -So far, most effort has been focused on the `efile_drv.c` code, -which implements most file I/O on behalf of the Erlang virtual -machine. This driver also presents a big challenge: its use of an I/O -worker pool (enabled by using the `erl +A 8` flag, for example) makes -it much more difficult to trace I/O activity because each of the -following may be executed in a different Pthread: - -* I/O initiation (Erlang code) -* I/O proxy process handling, e.g. read/write when file is not opened - in `raw` mode, operations executed by the code & file server processes. - (Erlang code) -* `efile_drv` command setup (C code) -* `efile_drv` command execution (C code) -* `efile_drv` status return (C code) - -Example output from `lib/runtime_tools/examples/efile_drv.d` while executing -`file:rename("old-name", "new-name")`: - - efile_drv enter tag={3,84} user tag some-user-tag | RENAME (12) | args: old-name new-name ,\ - 0 0 (port #Port<0.59>) - async I/O worker tag={3,83} | RENAME (12) | efile_drv-int_entry - async I/O worker tag={3,83} | RENAME (12) | efile_drv-int_return - efile_drv return tag={3,83} user tag | RENAME (12) | errno 2 - -... where the following key can help decipher the output: - -* `{3,83}` is the Erlang scheduler thread number (3) and operation - counter number (83) assigned to this I/O operation. Together, - these two numbers form a unique ID for the I/O operation. -* `12` is the command number for the rename operation. See the - definition for `FILE_RENAME` in the source code file `efile_drv.c` - or the `BEGIN` section of the D script `lib/runtime_tools/examples/efile_drv.d`. -* `old-name` and `new-name` are the two string arguments for the - source and destination of the `rename(2)` system call. - The two integer arguments are unused; the simple formatting code - prints the arguments anyway, 0 and 0. -* The worker pool code was called on behalf of Erlang port `#Port<0.59>`. -* The system call failed with a POSIX errno value of 2: `ENOENT`, - because the path `old-name` does not exist. -* The `efile_drv-int_entry` and `efile_drv_int_return` probes are - provided in case the user is - interested in measuring only the latency of code executed by - `efile_drv` asynchronous functions by I/O worker pool threads - and the OS system call that they encapsulate. - -So, where does the `some-user-tag` string come from? - -At the moment, the user tag comes from code like the following: - - dyntrace:put_tag("some-user-tag"), - file:rename("old-name", "new-name"), - -This method of tagging I/O at the Erlang level is subject to change. - -Example DTrace probe specification ----------------------------------- - - /** - * Fired when a message is sent from one local process to another. - * - * NOTE: The 'size' parameter is in machine-dependent words and - * that the actual size of any binary terms in the message - * are not included. - * - * @param sender the PID (string form) of the sender - * @param receiver the PID (string form) of the receiver - * @param size the size of the message being delivered (words) - * @param token_label for the sender's sequential trace token - * @param token_previous count for the sender's sequential trace token - * @param token_current count for the sender's sequential trace token - */ - probe message__send(char *sender, char *receiver, uint32_t size, - int token_label, int token_previous, int token_current); - - /** - * Fired when a message is sent from a local process to a remote process. - * - * NOTE: The 'size' parameter is in machine-dependent words and - * that the actual size of any binary terms in the message - * are not included. - * - * @param sender the PID (string form) of the sender - * @param node_name the Erlang node name (string form) of the receiver - * @param receiver the PID/name (string form) of the receiver - * @param size the size of the message being delivered (words) - * @param token_label for the sender's sequential trace token - * @param token_previous count for the sender's sequential trace token - * @param token_current count for the sender's sequential trace token - */ - probe message__send__remote(char *sender, char *node_name, char *receiver, - uint32_t size, - int token_label, int token_previous, int token_current); - - /** - * Fired when a message is queued to a local process. This probe - * will not fire if the sender's pid == receiver's pid. - * - * NOTE: The 'size' parameter is in machine-dependent words and - * that the actual size of any binary terms in the message - * are not included. - * - * @param receiver the PID (string form) of the receiver - * @param size the size of the message being delivered (words) - * @param queue_len length of the queue of the receiving process - * @param token_label for the sender's sequential trace token - * @param token_previous count for the sender's sequential trace token - * @param token_current count for the sender's sequential trace token - */ - probe message__queued(char *receiver, uint32_t size, uint32_t queue_len, - int token_label, int token_previous, int token_current); - - /** - * Fired when a message is 'receive'd by a local process and removed - * from its mailbox. - * - * NOTE: The 'size' parameter is in machine-dependent words and - * that the actual size of any binary terms in the message - * are not included. - * - * @param receiver the PID (string form) of the receiver - * @param size the size of the message being delivered (words) - * @param queue_len length of the queue of the receiving process - * @param token_label for the sender's sequential trace token - * @param token_previous count for the sender's sequential trace token - * @param token_current count for the sender's sequential trace token - */ - probe message__receive(char *receiver, uint32_t size, uint32_t queue_len, - int token_label, int token_previous, int token_current); - - /* ... */ - - /* Async driver pool */ - - /** - * Show the post-add length of the async driver thread pool member's queue. - * - * NOTE: The port name is not available: additional lock(s) must - * be acquired in order to get the port name safely in an SMP - * environment. The same is true for the aio__pool_get probe. - * - * @param port the Port (string form) - * @param new queue length - */ - probe aio_pool__add(char *, int); - - /** - * Show the post-get length of the async driver thread pool member's queue. - * - * @param port the Port (string form) - * @param new queue length - */ - probe aio_pool__get(char *, int); - - /* Probes for efile_drv.c */ - - /** - * Entry into the efile_drv.c file I/O driver - * - * For a list of command numbers used by this driver, see the section - * "Guide to probe arguments" in ../../../README.md. That section - * also contains explanation of the various integer and string - * arguments that may be present when any particular probe fires. - * - * TODO: Adding the port string, args[10], is a pain. Making that - * port string available to all the other efile_drv.c probes - * will be more pain. Is the pain worth it? If yes, then - * add them everywhere else and grit our teeth. If no, then - * rip it out. - * - * @param thread-id number of the scheduler Pthread arg0 - * @param tag number: {thread-id, tag} uniquely names a driver operation - * @param user-tag string arg2 - * @param command number arg3 - * @param string argument 1 arg4 - * @param string argument 2 arg5 - * @param integer argument 1 arg6 - * @param integer argument 2 arg7 - * @param integer argument 3 arg8 - * @param integer argument 4 arg9 - * @param port the port ID of the busy port args[10] - */ - probe efile_drv__entry(int, int, char *, int, char *, char *, - int64_t, int64_t, int64_t, int64_t, char *); - - /** - * Entry into the driver's internal work function. Computation here - * is performed by a async worker pool Pthread. - * - * @param thread-id number - * @param tag number - * @param command number - */ - probe efile_drv__int_entry(int, int, int); - - /** - * Return from the driver's internal work function. - * - * @param thread-id number - * @param tag number - * @param command number - */ - probe efile_drv__int_return(int, int, int); - - /** - * Return from the efile_drv.c file I/O driver - * - * @param thread-id number arg0 - * @param tag number arg1 - * @param user-tag string arg2 - * @param command number arg3 - * @param Success? 1 is success, 0 is failure arg4 - * @param If failure, the errno of the error. arg5 - */ - probe efile_drv__return(int, int, char *, int, int, int); - -Guide to efile_drv.c probe arguments ------------------------------------- - - /* Driver op code: used by efile_drv-entry arg3 */ - /* used by efile_drv-int_entry arg3 */ - /* used by efile_drv-int_return arg3 */ - /* used by efile_drv-return arg3 */ - - #define FILE_OPEN 1 (probe arg3) - probe arg6 = C driver dt_i1 = flags; - probe arg4 = C driver dt_s1 = path; - - #define FILE_READ 2 (probe arg3) - probe arg6 = C driver dt_i1 = fd; - probe arg7 = C driver dt_i2 = flags; - probe arg8 = C driver dt_i3 = size; - - #define FILE_LSEEK 3 (probe arg3) - probe arg6 = C driver dt_i1 = fd; - probe arg7 = C driver dt_i2 = offset; - probe arg8 = C driver dt_i3 = origin; - - #define FILE_WRITE 4 (probe arg3) - probe arg6 = C driver dt_i1 = fd; - probe arg7 = C driver dt_i2 = flags; - probe arg8 = C driver dt_i3 = size; - - #define FILE_FSTAT 5 (probe arg3) - probe arg6 = C driver dt_i1 = fd; - - #define FILE_PWD 6 (probe arg3) - none - - #define FILE_READDIR 7 (probe arg3) - probe arg4 = C driver dt_s1 = path; - - #define FILE_CHDIR 8 (probe arg3) - probe arg4 = C driver dt_s1 = path; - - #define FILE_FSYNC 9 (probe arg3) - probe arg6 = C driver dt_i1 = fd; - - #define FILE_MKDIR 10 (probe arg3) - probe arg4 = C driver dt_s1 = path; - - #define FILE_DELETE 11 (probe arg3) - probe arg4 = C driver dt_s1 = path; - - #define FILE_RENAME 12 (probe arg3) - probe arg4 = C driver dt_s1 = old_name; - probe arg5 = C driver dt_s2 = new_name; - - #define FILE_RMDIR 13 (probe arg3) - probe arg4 = C driver dt_s1 = path; - - #define FILE_TRUNCATE 14 (probe arg3) - probe arg6 = C driver dt_i1 = fd; - probe arg7 = C driver dt_i2 = flags; - - #define FILE_READ_FILE 15 (probe arg3) - probe arg4 = C driver dt_s1 = path; - - #define FILE_WRITE_INFO 16 (probe arg3) - probe arg6 = C driver dt_i1 = mode; - probe arg7 = C driver dt_i2 = uid; - probe arg8 = C driver dt_i3 = gid; - - #define FILE_LSTAT 19 (probe arg3) - probe arg4 = C driver dt_s1 = path; - - #define FILE_READLINK 20 (probe arg3) - probe arg4 = C driver dt_s1 = path; - - #define FILE_LINK 21 (probe arg3) - probe arg4 = C driver dt_s1 = existing_path; - probe arg5 = C driver dt_s2 = new_path; - - #define FILE_SYMLINK 22 (probe arg3) - probe arg4 = C driver dt_s1 = existing_path; - probe arg5 = C driver dt_s2 = new_path; - - #define FILE_CLOSE 23 (probe arg3) - probe arg6 = C driver dt_i1 = fd; - probe arg7 = C driver dt_i2 = flags; - - #define FILE_PWRITEV 24 (probe arg3) - probe arg6 = C driver dt_i1 = fd; - probe arg7 = C driver dt_i2 = flags; - probe arg8 = C driver dt_i3 = size; - - #define FILE_PREADV 25 (probe arg3) - probe arg6 = C driver dt_i1 = fd; - probe arg7 = C driver dt_i2 = flags; - probe arg8 = C driver dt_i3 = size; - - #define FILE_SETOPT 26 (probe arg3) - probe arg6 = C driver dt_i1 = opt_name; - probe arg7 = C driver dt_i2 = opt_specific_value; - - #define FILE_IPREAD 27 (probe arg3) - probe arg6 = C driver dt_i1 = fd; - probe arg7 = C driver dt_i2 = flags; - probe arg8 = C driver dt_i3 = offsets[0]; - probe arg9 = C driver dt_i4 = size; - - #define FILE_ALTNAME 28 (probe arg3) - probe arg4 = C driver dt_s1 = path; - - #define FILE_READ_LINE 29 (probe arg3) - probe arg6 = C driver dt_i1 = fd; - probe arg7 = C driver dt_i2 = flags; - probe arg8 = C driver dt_i3 = read_offset; - probe arg9 = C driver dt_i4 = read_ahead; - - #define FILE_FDATASYNC 30 (probe arg3) - probe arg6 = C driver dt_i1 = fd; - - #define FILE_FADVISE 31 (probe arg3) - probe arg6 = C driver dt_i1 = fd; - probe arg7 = C driver dt_i2 = offset; - probe arg8 = C driver dt_i3 = length; - probe arg9 = C driver dt_i4 = advise_type; +Probe specifications can be found in `erts/emulator/beam/erlang_dtrace.d`, and +a few example scripts can be found under `lib/runtime_tools/examples/`. [1]: http://www.erlang.org/euc/08/ [$ERL_TOP/HOWTO/SYSTEMTAP.md]: SYSTEMTAP.md |