TotalView Users Guide - CI Wiki

Examining Groups
Manipulating Processes and Threads
When you debug a multi-process program, TotalView adds processes to
both a control and a share group as the process starts. These groups are
not related to either UNIX process groups or PVM groups. (See Chapter 2,
“About Threads, Processes, and Groups,” on page 15 for information on groups.)
Because a program can have more than one control group and more than
one share group, TotalView decides where to place a process based on the
type of system call—which can either be fork() or execve()—that created or
changed the process. The two types of process groups are:
Control Group The parent process and all related processes. A control
group includes children that a process forks (processes
that share the same source code as the parent).
It also includes forked children that subsequently call a
function such as execve(). That is, a control group can
contain processes that don’t share the same source
code as the parent.
Control groups also include processes created in parallel
programming disciplines like MPI.
Share Group The set of processes in a control group that shares the
same source code. Members of the same share group
share action points.
See Chapter 13, “Using Groups, Processes, and Threads,” on page 251 for a complete
discussion of groups.
TotalView automatically creates share groups when your processes fork children
that call the execve() function, or when your program creates processes
that use the same code as some parallel programming models such as MPI
do.
TotalView names processes according to the name of the source program,
using the following naming rules:
� TotalView names the parent process after the source program.
� The name for forked child processes differs from the parent in that
TotalView appends a numeric suffix (.n). If you’re running an MPI program,
the numeric suffix is the process’s rank in COMM_WORLD.
� If a child process calls the execve() function after it is forked, TotalView
places a new executable name in angle brackets ().
In the following figure, assume that the generate process doesn’t fork any
children, and that the filter process forks two child processes. Later, the
first child forks another child, and then calls the execve() function to execute
the expr program. In this figure, the middle column shows the names
that TotalView uses. (See Figure 152 on page 236.
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