.MA - Format Memory Arena Records (VMAR)

Display memory arena records (VMARs). Optionally format related object records (VMOBs), alias records (VMALs) and context records (VMCOs).

Syntax:

────.MA ──┬─┬───────────────┬─┬───────┬─┬───────────┬─────────
            │ ├── M  ─┬───────┤ └── C ──┘ └── maddr ──┘
            │ │       └── A ──┤
            │ └────── A ──────┘
            │
            └─┬───────┬─┬─────────────────────┬──────────────────
              └── B ──┘ ├────────── F ────────┤
                        └─┬───────┬─┬───────┬─┘
                          ├── L ──┤ └── C ──┘
                          ├── R ──┤
                          └── H ──┘

───────────────────────┬───────────────────────────┬───────────
                        ├── har ────┬──┬─────────┬──┘
                        └── laddr ──┘  └── L n ──┘

Parameters:

A

This is option is used with (and implies) the M option. It causes the a match for private area addresses to be made across all contexts. See the M option for further details.

Note:

Under Kernel Debugger the default is to match addresses in the current context only.

Under Dump Formatter address matches are made across all contexts, that is the A option is in permanent effect.

B
Display in-use (busy) arena records in sequential order.
C
Display chained memory structures.

Chaining causes related memory structures to be displayed in groups, the head of which is indicated by an * suffix. The related structures are:

aliases to the associated arena record (VMALs).
arena records of all associated alias records (VMARs).
shared instance data objects for all related arena records
context records for shared objects of all associated arena records (VMCOs). See .MC command.
object records of all associated arena records (VMOBs). See .MO command.
F
Display free arena records.
H
Follow the arena hash chain pointer. The hash chain is used by virtual memory management to look up a memory object for a given context from a linear address. The algorithm proceeds as follows:

The linear address is bitwise ANDed with the hash table mask obtained from at_lHashNumbMask (VMAT+0x14). The result is shifted right by the allocation granularity for the arena. This is obtained from at_lHashNumbShift (VMAT+0x18). The result provides an index into the hash table, which is a table of arena handles that head each hash chain. The hash table address is obtained from ah_paharHash (VMAH+0x14) and the VMAT address is obtained from ah_pat (VMAH+0x18).

For OS/2 Warp V3.0, the hashing algorithm amounts to the following:

System Arena:

index=(linear address >> 0x0c) & 0x1ff
Tiled Shared and Private arenas:
index=(linear address >> 0x10) & 0x1ff
VDM Private arenas:
index=(linear address >> 0x0c) & 0x1ff
L
Follow the arena forward (left) chain pointer. Arena records for each arena are chained using a double-linked circular chain. The Dump Formatter or Kernel Debugger will not detect wrap-around. This option must therefore be limited by specifying a fixed number of arena records, using the Ln operand, or interrupted using Ctrl+C.
M
Searches for all arena records (of all contexts) that represent virtual memory that encloses the address specified in maddr If maddr is not specified then the current CS:EIP is taken as the matching address. If the storage is in the private arena Kernel Debugger will search the current context only unless the

An address expression may be specified. A option is specified. The Dump Formatter always searches for matches in all contexts.

R
Follow the arena backward (right) chain pointer. Arena records for each arena are chained using a double-linked circular chain. The Dump Formatter or Kernel Debugger will not detect wrap-around. This option must therefore be limited by specifying a fixed number of arena records, using the Ln operand, or interrupted using Ctrl+C.
maddr
Specifies the matching address to be used with the M option.
laddr
Specifies the linear address of a specific arena record to be formatted.
Ln
Specifies the number of arena records to display.
har
Specifies the handle of a specific arena record to be formatted.

Results & Notes:

Arena records are in contiguous storage, which is anchored from the address given by global variable:

_parvmOne

Output from the .MA command is formatted using a common template with minor variations.

Note: Because a common display template is used for all forms of arena record certain fields will be irrelevant to the records being viewed and may contain garbage information. Specific cases are noted in the examples where this applies.

The following are example of the nine formats of area record:

Free Arena Record
Sentinel Arena Record
Boundary Sentinel Arena Record
System Arena Records mapped by GDT selectors
System Arena Records not mapped by GDT selectors
Shared Arena Records for Shared Data
Shared Arena Records for Instance Data
Private Arena Records for non-shared Data
Private Arena Records for shared Data

For a description of the fields formatted by .MA select .MA Output Field Descriptions

For more examples using of the .M family of commands see: Exploring Memory Management.

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