This call sets up a signal handler that is invoked every 10
seconds by an
interrupt. Inside, it evaluates how much memory it can allocate and
associates
it with the callstack. The user can vary the size of the callstack by
setting
the environment variable TAU_CALLSTACK_DEPTH (default is 2).
The examples/headroom/track subdirectory has an example that
illustrates the
use of this call. To disable tracking this headroom at runtime, the
user
may call:
TAU_DISABLE_TRACKING_MEMORY_HEADROOM() and call
TAU_ENABLE_TRACKING_MEMORY_HEADROOM() to re-enable
tracking of the headroom.
To set a different interrupt interval, call
TAU_SET_INTERRUPT_INTERVAL(value)
where value (in seconds) represents the inter-interrupt interval.
A sample profile generated has:
USER EVENTS Profile :NODE 0, CONTEXT 0, THREAD 0
---------------------------------------------------------------------------------------
NumSamples MaxValue MinValue MeanValue Std. Dev. Event Name
---------------------------------------------------------------------------------------
3 4067 4061 4065 2.828 Memory Headroom Left (in
MB)
3 4067 4061 4065 2.828 Memory Headroom
Left (in MB) : void quicksort(int *, int, int) => void
quicksort(int *, int, int)
--------------------------------------------------------------------------------
Sometimes it is useful to track the memory available at a certain
point in the
program, rather than rely on an interrupt.
TAU_TRACK_MEMORY_HEADROOM_HERE()
allows us to examine the memory available at a particular location in
the source
code and associate it with the currently executing callstack.
The examples/headroom/here subdirectory has an example that illustrates
this usage.
ary = new double [1024*1024*50];
TAU_TRACK_MEMORY_HEADROOM_HERE(); /* takes a sample here! */
sleep(1);
A sample profile looks like this:
USER EVENTS Profile :NODE 0, CONTEXT 0, THREAD 0
---------------------------------------------------------------------------------------
NumSamples MaxValue MinValue MeanValue Std. Dev. Event Name
---------------------------------------------------------------------------------------
3 3672 3672 3672 0 Memory Headroom Left (in
MB)
1 3672 3672 3672 0 Memory Headroom
Left (in MB) : main() (calls f1, f5) => f1() (sleeps 1 sec,
calls f2, f4)
1 3672 3672 3672 0 Memory
Headroom Left (in MB) : main() (calls f1, f5) => f1()
(sleeps 1 sec, calls f2, f4) => f4() (sleeps 4 sec,
calls f2)
1 3672 3672 3672 0 Memory Headroom Left
(in MB) : main() (calls f1, f5) => f5() (sleeps 5 sec)
---------------------------------------------------------------------------------------
By setting the enviroment variable
TAU_TRACK_HEADROOM=1, a sample is taken at instrumented function's
entry and
associated with the function name. This option is meant to be used as a
debugging aid due the high cost associated with executing a series of
malloc
calls. The cost was 106 microseconds on an IBM BG/L (700 MHz CPU). The examples/headroom/available subdirectory has a simple
example that
produces the following profile when TAU is configured with the
TAU_TRACK_HEADROOM option set.
USER EVENTS Profile :NODE 0, CONTEXT 0, THREAD 0
---------------------------------------------------------------------------------------
NumSamples MaxValue MinValue MeanValue Std. Dev. Event Name
---------------------------------------------------------------------------------------
1 4071 4071 4071 0 f1() (sleeps 1 sec,
calls f2, f4) - Memory Headroom Available (MB)
2 3671 3671 3671 0 f2() (sleeps 2
sec, calls f3) - Memory Headroom Available (MB)
2 3671 3671 3671 0 f3() (sleeps 3 sec) -
Memory Headroom Available (MB)
1 3671 3671 3671 0 f4() (sleeps 4 sec,
calls f2) - Memory Headroom Available (MB)
1 3671 3671 3671 0 f5() (sleeps 5 sec) -
Memory Headroom Available (MB)
1 4071 4071 4071 0 main() (calls f1, f5)
- Memory Headroom Available (MB)
---------------------------------------------------------------------------------------