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Cisco Bug: CSCvh76003 - I/O memory leak with SCP messages destined to Port Manager

Last Modified

Sep 17, 2019

Products (1)

  • Cisco Catalyst 6000 Series Switches

Known Affected Releases


Description (partial)

A rapid I/O memory leak is observed on the active supervisor of a Catalyst 6500 chassis. This is observed in the Small, Medium and Big buffer pools:

<pre>Small buffers, 104 bytes (total 6144, permanent 6144):
     3787 in free list (2048 min, 8192 max allowed)   <-------------------------------------- many buffers consumed from freelist
     719388488 hits, 0 misses, 0 trims, 0 created
     0 failures (0 no memory)
Medium buffers, 256 bytes (total 10792, permanent 3000, peak 10792 @ 00:00:48):   <---------- huge current/peak value
     83 in free list (64 min, 3000 max allowed)
     20712651 hits, 3216 misses, 517 trims, 8309 created
     0 failures (0 no memory)
Big buffers, 1536 bytes (total 84503, permanent 1000, peak 84503 @ 00:00:00):   <------------ huge current/peak value
     75 in free list (64 min, 2000 max allowed)
     107897976 hits, 37586 misses, 1082 trims, 84585 created
     0 failures (0 no memory)</pre>

The 'show buffers usage' output will show that the vast majority of these leaked buffers are associated with SCP (Serial Control Protocol) messages, with opcodes 0x1E, 0x1204 and 0x14A. SCP is an internal communication protocol used for messages between processes and modules on the switch. An example from the Big buffers pool:

<pre>Pool: Big

Non ipc/scp link type count: 1018

------SCP USAGE------
Dsap  Ssap  Opcode  Count
0x1   0x0   0x1E    58857  <--------- many buffers under one of a few opcodes
0x1   0x0   0x1204   4745
0x1   0x2   0x1E    11323
0x1   0x0   0x14A   8479
0x1E  0x0   0x205   9
0x1E  0x2   0x205   1
Non-aligned packet(s): 3
 Caller Summary
    pc = 0x500E6D4              count = 84425   <--------------------- majority buffers under one allocator
    pc = 0x91DF708              count = 1
    pc = 0x8FE2CF8               count = 1

The leak is known to occur if both supervisors are inserted into the chassis. If one supervisor is removed, the leak will stop.

The exact conditions needed to trigger the leak are not known at this time.
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