Hi
all,
I'm looking to implement new features
in TMF about filter
expressions using the state system. I would appreciate receiving
your feedback on the proposal.
Currently, we can only specify constraints on the event context and
payload.
For example : event_type == sys_read && fd == 3
- Specify filter _expression_ using state information
The first feature is to add the use of state system attributes, to
be mixed with payload and context information. For example : /event/type
== "sys_read" && /system/${/event/pid}/files/${/event/fd}/pathname
== "/etc/passwd"
I want to propose a syntax to make this _expression_. The nodes in the
attribute tree are referenced using a hierarchical path. This path
is a sequence of names and can be expressed with the usual notation,
e.g. /processes/cpu/state. Each path component can be a constant
string, or a quoted string to escape special characters.
Alternatively a component can also be a number which is the put in
[]. This is used for directory nodes where all childs use integers
as names, which is more efficient than treating numbers as strings
and using strings. Finally, a component can be a variable where the
value of the component is obtained by referencing a path; the $
notation is used as in shell scripts. We use the C/Java syntax, '=='
to compare and '=' to assign.
/processes/[4]/state == RUNNING
/processes/[4]/state_start_time ==
012032432
/processes/[4]/PPID == 1
/processes/[4]/user_mode/cumulative_time ==
5789357
/cpu/[0]/current_process == /processes/[1]
/processes/[${/processes/[4]/PPID}]/childs_cumulative_time
The model of the attribute tree is extended to make available as
well some dynamically computed information related to the current
context (channel, event). This additional information is not
assigned nor saved in the history tree. For example, some
information is associated with the current channel such as the CPU.
In addition, all the fields of the current event as well are made
available through the attribute tree syntax. For example, the
following information may be accessed through the associated paths.
/event/timestamp
/event/type
/event/TID
/event/CPU
/event/field/next_process
/event/field/poll_array/[4]
These values can be used in logical and arithmetic expressions for
expressing conditions or assignments. Conditions are primarily used
in filters, for example in the detailed event list view. They are
also used as guards for state changes or as trigger for creating
abstract events.
- Specify
expressions to determine state entry / exit
The second feature is to provide _expression_ for state change.
Currently
this logic is coded in Java in files such as :
org.eclipse.linuxtools.lttng2.kernel.core/src/org/eclipse/linuxtools/internal/lttng2/kernel/core/stateprovider/CtfKernelStateInput.java
It would
be nice to be able to provide expressions for that. This
way, adding state for specific needs would not require
programming and we could import/export new types of state
systems easily (as part of the CTF metadata for example).
Upon event of type sys_open:
/processes/${/event/pid}/files/${/event/fd}/pathname
= name
/processes/${/event/pid}/files/${/event/fd}/mode
= mode
Once we can easily refer to state
using such expressions, several additional features become
relatively easy to add such as new "virtual" columns in the
detailed event list computed based on an _expression_ instead
of being "event context" or "payload information". In
addition, such expressions could become part of the CTF
metadata to describe states, state entry expressions, colors
to associate with specific states in the control flow
view...
I would like to have the
developers' opinion on these two features. Do you see any major
problem or easy simplification for this syntax?
Thanks,
Florian
------------------------------------------------------------------------------------------------
Complete examples for transcription of the CtfKernetStateInput.java
:
case 1: // "exit_syscall":
/* Clear the current system call on the process */
/Threads/[${/CPUs/[${/event/Cpu}]/Current_thread}]/System_call =
NULL
/* Put the process' status back to user mode */
/Threads/[${/CPUs/[${/event/Cpu}]/Current_thread}]/Status =
PROCESS_STATUS_RUN_USERMODE
/* Put the CPU's status back to user mode */
/CPUs/[${/event/Cpu}]/Status = CPU_STATUS_RUN_USERMODE
case 8: // "sched_process_fork":
/* Assign the PPID to the new process */
/Threads/[${/event/child_tid}]/PPID = /event/parent_tid
/* Set the new process' exec_name */
/Threads/[${/event/child_tid}]/Exec_name = /event/child_comm
/* Set the new process' status */
/Threads/[${/event/child_tid}]/Status = PROCESS_STATUS_WAIT_FOR_CPU
/* Set the process' syscall name, to be the same as the parent's */
/Threads/[${/event/child_tid}]/System_call =
/Threads/[${/event/parent_tid}]/System_call
case 11: // "lttng_statedump_process_state":
/* Set the process' name */
if( /Threads/[/event/tid]/Exec_name == Null)
/Threads/[/event/tid]/Exec_name = /event/name
/* Set the process' PPID */
if( /Threads/[/event/tid]/PPID == Null)
/Threads/[/event/tid]/PPID = /event/ppid
/* Set the process' status */
if( /Threads/[/event/tid]/Status == Null)
if(/event/status == 2)
/Threads/[/event/tid]/Status = PROCESS_STATUS_WAIT_FOR_CPU
else if(/event/status == 5)
/Threads/[/event/tid]/Status = PROCESS_STATUS_WAIT_BLOCKED
else
/Threads/[/event/tid]/Status = PROCESS_STATUS_UNKNOWN
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