Resolving Process Memory Problems - Cisco CRS-1 - Carrier Routing System Router Troubleshooting Manual

Chapter 9 Troubleshooting Memory
The show memory compare start command takes the initial snapshot of heap memory usage for all
processes on the router and sends the report to a temporary file. The show memory compare end
command takes the second snapshot of heap memory usage for all processes on the router and sends the
report to a temporary file. The snapshot taken with the show memory compare end command is
compared with the initial snapshot when displaying the heap memory usage comparison report using the
show memory compare report command. The show memory compare report command displays the
heap memory comparison report. The output from the show memory compare report command
displays details about heap memory usage for all processes on the router at different moments in time
and compares the results (compares the amount of memory allocated and deallocated during a session).
The report contains information about each process whose heap memory usage has changed from the
time the first and second snapshots were taken. The process with the largest memory difference is listed
first. The memory usage analyzer should be used on a stable system when no configuration changes are
in progress.

Resolving Process Memory Problems

The following conditions can be the cause of process memory problems:
•
•
•
•
OL-21483-02
Memory leak—Occurs when a process requests or allocates memory and then forgets to free
(deallocate) the memory when finished with that task. As a result, the memory block is reserved until
the router is reloaded. Over time, more and more memory blocks are allocated by that process until
there is no free memory available.
To detect a memory leak, use the show memory compare end and show memory compare report
commands multiple times at regular intervals (either at set hours or once each day). The first show
memory compare start command creates the process comparison table. If the difference for a
specific process is constantly increasing (a process that should not be increasing), a memory leak is
probable. Restart the process to free the memory and stop the memory leak using the process restart
job-id location node-id command. If a process restart does not resolve the memory leak problem,
contact Cisco Technical Support. For Cisco Technical Support contact information, see the
"Obtaining Documentation and Submitting a Service Request" section on page viii
Large quantity of memory used for normal or abnormal processes—A normal or abnormal event (for
example, a large routing instability) causes the router to use an unusually large amount of processor
memory for a short period of time, during which the memory has run out. The memory shortage may
also be due to a combination of factors, such as:
A memory leak that has consumed a large amount of memory, and then a network instability
–
pushes the free memory to zero.
The router does not have enough memory to begin with, but the problem is discovered only
–
during a rare network event.
If the large memory usage is due to a normal event, install more memory. But, if the large memory
usage is due to an abnormal event, fix the related problem.
Dead process—A dead process is not a real process. The process is there to account for the memory
allocated under the context of another process that has terminated. Restart the process if you suspect
that it may be a real process, restart the process using the process restart job-id location node-id
command. If it is not a real process or if it is a real process and it does not restart, contact Cisco
Technical Support. For Cisco Technical Support contact information, see the
Documentation and Submitting a Service Request" section on page viii
Memory fragmentation—A process has consumed a large amount of processor memory and then
released most or all of it, leaving fragments of memory still allocated either by the process or by
other processes that allocated memory during the problem. If the same event occurs several times,
Cisco IOS XR Troubleshooting Guide for the Cisco CRS-1 Router
Troubleshooting Process Memory
in the Preface.
"Obtaining
in the Preface.
9-207