setmemwindow(1M)setmemwindow(1M)NAMEsetmemwindow - change window ID of running program or start program in
particular memory window
SYNOPSIS
WinId] { | program [arg]... }
DESCRIPTION
is the command that changes the window ID of a running process or
starts a specified program in a particular memory window.
If the option is specified with a nonzero pid, only the process's win‐
dow ID is changed, and any value specified for program is ignored.
The executable program is only executed if the process ID pid is either
or unspecified.
Changing the window ID for the running process does not mean the
process immediately attaches to or creates objects using that window.
The targeted process does not begin using the window until it executes
a new image.
used as a wrapper for an existing executable, starts the program in the
desired (see option below) memory window. In order to execute program,
changes the window ID, forks a child and executes program in the child
process. The default behavior of is to wait until program finishes.
If is specified, the waiting for program is bypassed and exits immedi‐
ately after forking the child.
If and are unspecified, the default behavior is to place the process
into the window specified by WinId. If WinId exists, then the process
is placed into that memory window. If no window exists with WinId, an
unused window is allocated and associated with WinId. specifies the
creation of a window. If the window already exists and is specified,
the call fails. specifies the joining to an existing window. If the
window does not exist and is specified, the call fails.
The option instructs the command to execute program even if is unable
to change the process's window to the specified WinId. The failure to
create a specific window may be the effect of the lack of available
memory windows; that is, the underlying kernel:
· Has not been configured with enough memory windows (exit status
· Was unable to allocate memory for a new window to meet this
request (exit status or
· Does not implement the feature (exit status
Options
Create a memory window where both memory window quadrants use
the same space ID. For executables this generates two
quadrants with the same space ID. Applications can use
this to generate the appearance of larger contiguous
shared memory ranges with a maximum of 2 gigabytes. For
example, an application that generates a 1 gigabyte
shared memory segment has that segment placed into the
2nd quadrant by default. If the application creates
another 1 gigabyte segment that segment is placed in the
3rd quadrant. Both segments are contiguous virtually,
allowing the application to treat the virtual range as
if it were a contiguous 2 gigabyte segment.
This option only benefits executables. They are the
only type of executable format able to place shared
objects in the 2nd quadrant.
Create a window with ID
WinId and attach the specified process to it. If WinId
already exists the call fails.
The default behavior for
is to exit without executing the user specified program
if the memory window cannot be set. The failure to set
the memory window may be caused by:
· The lack of enough memory windows in the system.
· The memory windows feature is not implemented.
· The request requires a new memory window be ini‐
tialized and the system was not able to allocate
the memory to do so.
· A memory window with WinId could not be found in
the attempt to join a memory window.
· A memory window with the WinId was found in the
attempt to create a memory window.
The option instructs to execute program whether the
desired memory window was set or not. Obviously, using
this option there is no guarantee program has been
attached to the desired memory window and it is unclear
in what memory window it is running. Using this option
is strongly discouraged.
Specifies the desired memory window.
WinId is a key to the desired memory window. WinId is a
user specified value and should be one of the values
contained in the file
Applications extract the user key from according to a
unique string contained in using the command. (See get‐
memwindow(1M) and services.window(4).)
The kernel tries to locate an existing window with
WinId. If one is found, that window is used. If no
window with WinId is found, an unused entry is located
and assigned to WinId.
The value for WinID is special. If specified, the
process/program is placed into the default global window
instead of a unique window with ID WinId.
If WinID is unspecified, the process and its children
will run in a private memory window, and no other pro‐
cesses in the system can attach to this memory window.
This memory window remains active until the process and
its children terminate.
Join an existing window with ID
WinId. The specified process attaches to an existing
memory window. If no entry exists the call fails.
If program is executed, the default behavior is to (see the
wait(2) manual page) for the process to terminate.
Specifying causes to exit after forking the child (that
will execute program).
Send the PID of the executed
program to standard output. The message sent out is:
where dddd is the decimal value of the PID.
Change the memory window for process
pid, or start program in the specified memory window.
If program has arguments (arg ...), they must also be
specified.
If is unspecified or the value of pid is the calling
process has its window ID changed, and program is exe‐
cuted.
If a nonzero process pid is specified, only the window
in that process is changed, and program is ignored.
Execute in verbose (debug) mode.
Application Usage
Memory Windows helps alleviate the 1.75-gigabyte limitation on system-
wide shared memory for 32-bit applications by allowing cooperating
applications to configure their own 1-gigabyte window of shared
resources.
The definition of a memory window is only available for 32-bit pro‐
cesses.
Note that memory windows allows the creation of more than 1.75 giga‐
bytes of total system-wide shared memory, but it does not extend how
much shared memory a single process can create. executables are still
limited to 1.75 gigabytes.
HP-UX ships memory windows disabled. To enable memory windows, the
kernel tunable parameter, must be set to the desired number. repre‐
sents the number of memory windows beyond the global default window.
Setting to for example, would produce a total of three memory windows,
the default global window plus two user defined windows. Setting to
leaves only the default or global memory window.
There are two new commands and one file introduced by memory windows:
and file.
The file maps a memory window application to a particular window ID.
Using this central file allows applications to share memory windows, by
using the same window ID, as well as avoid unintentional memory window
collisions. See services.window(4) for more information.
The command is used to extract the window ID of a user process from the
file. The command starts a particular process in a memory window. A
common usage of these commands is to extract a memory window ID with
which is then passed to to start a process with the given window ID.
Processes must be in the same window to share data. Processes wanting
to share global data, such as shared memory or memory mapped files,
must make sure all processes are in the same memory window. If pro‐
cesses in different memory windows wish to share data reliably, the
creator of the data must take steps to guarantee the data is placed in
a location accessible to all processes.
For more detailed information on memory windows, refer to the
RETURN VALUE
The exit value is 0 on success or a positive number on failure.
If is not specified, the value is the exit status of the executed pro‐
gram, obtained from the system call.
EXAMPLES
Start the program in a memory window extracted by the string
Start the program in a newly created memory window extracted by the
string
Start the program in an existing memory window extracted by the string
Start the program in a private memory window. Only and its descendents
can access the window.
WARNINGS
Programs using a memory window can access shared memory objects created
by other programs using the same window (depending upon permissions).
However, by default, programs using a memory window may not be able to
access shared memory objects created by programs using other windows or
those not using windows at all.
To enable access to a shared memory object across programs using dif‐
ferent windows, or between those using windows and those not using win‐
dows, the program must specify special options when creating the
object. See shmget(2) and mmap(2) for details.
AUTHOR
was developed by HP.
FILES
File containing applications' associated window IDs.
SEE ALSOgetmemwindow(1M), services.window(4).
setmemwindow(1M)
