Information About the Buffer Utilization Histogram Feature
The Buffer Utilization Histogram feature enables you to analyze the maximum queue depths and buffer utilization in the system in real time. Instantaneous or real time buffer utilization information is supported by the hardware. You can use software to obtain the history of the buffer usage by polling the hardware at regular intervals. Obtaining an historic timeline of the buffer usage provides a better picture of the traffic pattern in the system and helps in traffic engineering. Ultimately, you are able to make better use of the hardware buffer resources.
On the Cisco Nexus device, every three ports of 40 Gigabit Ethernet or every 12 ports of 10 Gigabit Ethernet have access to a shared 25 Mb packet buffer. 15.6 Mb are reserved for ingress and 8.6 Mb are reserved for egress. The remaining space is used for SPAN and control packets.
The Buffer Utilization Histogram enables you to do the following:
Configure buffer utilization history measurements on the interested ports.
View buffer utilization over an interval of time.
Configure either a slow or a fast polling mode.
Copy collected statistics to the buffer_util_stats file on the bootflash drive every hour to allow for later analysis. The collected statistics are appended to the end of the file after an hour and a timestamp is placed in the header that has the interface name.