Cisco 3850: Process responsible for Softbuffers

Question

There is a command to increase the SoftMax Buffers on 3850 switches:

qos queue-softmax-multiplier 200

This is done in percent which means i am doubling the amount of softmax buffer.

Before, the SoftMax buffers for 10Gig interface are at 2000:

switch#sh platform hardware fed switch 2 qos queue config interface Te2/0/37
DATA Port:1 GPN:1425 AFD:Disabled QoSMap:0 HW Queues: 8 - 15
  DrainFast:Disabled PortSoftStart:3 - 4500
----------------------------------------------------------
   DTS  Hardmax  Softmax   PortSMin  GlblSMin  PortStEnd
  ----- --------  --------  --------  --------  ---------
 0   1  6   500   7  2000   7  1280   0     0   5  6000
 1   1  4     0   8  3000   8  1920   3   750   5  6000
 2   1  4     0   5     0   5     0   0     0   5  6000
 3   1  4     0   5     0   5     0   0     0   5  6000
 4   1  4     0   5     0   5     0   0     0   5  6000
 5   1  4     0   5     0   5     0   0     0   5  6000
 6   1  4     0   5     0   5     0   0     0   5  6000
 7   1  4     0   5     0   5     0   0     0   5  6000

After the command, they increased to 4000:

swRZ101#sh platform hardware fed switch 2 qos queue config interface Te2/0/37
DATA Port:1 GPN:1425 AFD:Disabled QoSMap:0 HW Queues: 8 - 15
  DrainFast:Disabled PortSoftStart:5 - 7500
----------------------------------------------------------
   DTS  Hardmax  Softmax   PortSMin  GlblSMin  PortStEnd
  ----- --------  --------  --------  --------  ---------
 0   1  6   500  12  4000   7  1280   0     0   7 10000
 1   1  4     0  13  6000   8  1920   3   750   7 10000
 2   1  4     0   5     0   5     0   0     0   7 10000
 3   1  4     0   5     0   5     0   0     0   7 10000
 4   1  4     0   5     0   5     0   0     0   7 10000
 5   1  4     0   5     0   5     0   0     0   7 10000
 6   1  4     0   5     0   5     0   0     0   7 10000
 7   1  4     0   5     0   5     0   0     0   7 10000

two questions arise from this:

• Are these bytes or queues or potatoes? I couldnt find anyting online.
• What about the ressources if i increase this to the max (12x) on the switch? Im guessing, these buffers are comming from the RAM. Is there a process where i can observe the memory usage not to overcommit anything? This is a stack of switches with 246 interfaces total.

Answer 1

Are these bytes or queues or potatoes? I couldnt find anyting online.

Cisco maintains documentation on its devices. For example, it took me about 30 seconds to find this by searching for cisco 3850 softmax buffer. I have higlighted the relavant text from Catalyst 3850: Troubleshooting Output drops:

The Default Buffer allocation for a 1GB port is 300 buffers and for a 10GB port, it is 1800 buffers (1 buffer = 256 bytes).

---

What about the ressources if i increase this to the max (12x) on the switch? Im guessing, these buffers are comming from the RAM. Is there a process where i can observe the memory usage not to overcommit anything? This is a stack of switches with 246 interfaces total.

Cisco has many different command variations to show the memory usage, from very detailed to general. For example:

show memory statistics

will show the processor and I/O (what you want) memory statistics in a condensed format. You can use the ? to see all the variations of the show memory command.