C H A P T E; Troubleshooting Memory; About Troubleshooting Memory - Cisco Nexus 9000 Series Troubleshooting Manual

Troubleshooting Memory

This chapter contains the following sections:
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About Troubleshooting Memory

Dynamic random access memory (DRAM) is a limited resource on all platforms and must be controlled or
monitored to ensure utilization is kept in check.
Cisco NX-OS uses memory in the following three ways:
• Page cache—When you access files from persistent storage (CompactFlash), the kernel reads the data
• Kernel—The kernel needs memory to store its own text, data, and Kernel Loadable Modules (KLMs).
• User processes—This memory is used by Cisco NX-OS or Linux processes that are not integrated in
When you are troubleshooting high memory utilization, you must first determine what type of utilization is
high (process, page cache, or kernel). Once you have identified the type of utilization, you can use additional
troubleshooting commands to help you figure out which component is causing this behavior.
About Troubleshooting Memory, page 69
General/High Level Assessment of Platform Memory Utilization, page 70
User Processes, page 70
Built-in Platform Memory Monitoring, page 71
into the page cache, which means that when you access the data in the future, you can avoid the slow
access times that are associated with disk storage. Cached pages can be released by the kernel if the
memory is needed by other processes. Some file systems (tmpfs) exist purely in the page cache (for
example, /dev/sh, /var/sysmgr, /var/tmp), which means that there is no persistent storage of this data and
that when the data is removed from the page cache, it cannot be recovered. tmpfs-cached files release
page-cached pages only when they are deleted.
KLMs are pieces of code that are loaded into the kernel (as opposed to being a separate user process).
An example of kernel memory usage is when an inband port driver allocates memory to receive packets.
the kernel (such as text, stack, heap, and so on).
C H A P T E R
Cisco Nexus 9000 Series NX-OS Troubleshooting Guide, Release 7.x
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