BrickOS Task and Memory Monitor

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BrickOS Task and Memory Monitor

• Charles Mancinelli
• CMPS 490
• Advisor Dr. Bi

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Review

• Constructing a monitor for the BrickOS.
• Java web applet using Swing components to build a
  GUI.
• Applet will monitor task/threads and the
  allocation in memory of those tasks.
• Information is sent from the RCX and received by
  PC by a USB infrared tower.
• LegOS Networking Protocol (LNP) to send
  addressing packets of data from the RCX.
• LNP is supported is implemented in Java by
  josx.rcxcomm package and also interfaces with USB.

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Overview of Presentation

• Representation
• Protocol
• Structure of Data Packets
• Data Structure
• Interface Design
• Architecture Design
• GUI Example
• Modifying the BrickOS

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Representation

• Integers only will be sent and received as
  packets.
• Java and C/C represent integers in four bytes.
• BrickOS integers are two bytes.
• (28)(28) 65536 words.
• Range of -32768 to 32767 signed.
• Shorten the representation to include a range of
  only positive integers.
• Range of 0 to 65535 unsigned which is the range
  of the memory layout of the RCX.

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Josx.rcxcomm Protocol

• Currently only supports sending a two byte buffer
  for addressing and integrity layers.
• Initial plan was to send an entire packet of
  integers associated with each process.
• Maximum size any packet can be is 255 bytes on
  both RCX and PC, Ive heard on 64 bytes can be
  sent reliably.
• Additional plan to modify the protocol to send
  packets of up to 255 bytes if there is time.
• Inherits the Javas input and output streams.

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Sending and Receiving Packets. RCX?PC

• RCX C program
• An array is initialized with two elements of type
  unsigned char. Each of which represent one byte.
• The unsigned integer is divide by 256 and placed
  in the 0 element of the array giving the higher
  order byte.
• It is then divided mod by 256 and placed in the
  1st element of the array giving the lower order
  byte.
• A system call is made to lnp_addressing_write.
• Java PC side
• A new instance of RCXLNPAddressingPort is
  initialized along with input stream and
  DataInputStream.
• An integer can then be read as a character
  because its 2 bytes.

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LNP Addressing Packets

• ----------------------------------------- 
  F1LENDESTSRC   ADATA      CHK 
  ----------------------------------------- 
                              
          lt-      IDATA        -gt
   
• F1    identifies an addressing packet 
  LEN   length of IDATA section ( 1 to 255
  bytes )  DEST  destination address  SRC  
  source address  ADATA payload data (1 to
  253 bytes)  .
• The Addressing packet is all set up by a simple
  system call.
• lnp_addressing_write(buffer, length, dest, recv)

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My Protocol

• How do you distinguish what type of data you are
  receiving on the PC if your getting a series of
  integers in a data stream?
• When the receiving module gets two negative
  integers it knows what type of packet it
  receives.
• -1 represents a task data.
• -2 represents memory data.
• -3 represents system information .

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What information will be displayed?

• Systems information which will include the
  version of the BrickOS running, the amount of
  memory used and free, and the number of task
  currently running on the system.
• Information for each task will include its
  priority, state, kernel/user, tid, pid, and the
  queue header.
• A layout of memory and where each task is
  displayed.

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Data Structure

• All packets of data received will be put into a
  doubly linked list.
• Three separate lists will be constructed for each
  type of data. Systems, memory or task data.
• Each packet of data will be stored as object of
  type memPacket, tcbPacket and sysPacket. Then it
  will be inserted into the appropriate list.

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Interface Design

• The Java look and feel will be used from Swing
  because it is compatible across all platforms.
• Functions and looks similar to the Task manger in
  Windows 98, 2000 or XP.
• Will contain a menu bar with file, control and
  help pull down menus.
• Three tabs where the information will be
  displayed called, System, Tasks and Memory Map.

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Architecture Design

• Architecture Diagram
• GUI Example

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Task Information
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Memory Information
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Modifying the BrickOS

• Modify the LNP to add the additional protocol I
  created for packets.
• When a task is run by the scheduler the
  information will be inserted into a packet. When
  the packet is full it will be sent using LNP.
  tm.c
• Modify mm.c to include a memory scan function
  that will give us the entire memory layout.

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Current Problems

• IR towers transmission might not be fast enough
  for it to operate in real time.
• Applets have to have special permission to read
  or write to files on an OS.
• The jos.rcxcomm package requires an operating
  systems dependant file. For Windows it requires
  irtower.dll.

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Any Questions, Comments or suggestions?