memory free low-watermark - threshold values?

[bruce.porter]

I have a 3750. What values do I use for the memory free low-watermark thresholds? Here are the outputs from the show memory:

sand5# sh mem

----------------Head---------Total(b)-------Used(b)-------Free(b)-------Lowest(b)-----Largest(b)

Processor----28B11B4----78966348----33108904----45857444----43916928----43879840

I/O-------------7400000-----12574720-----8637012-------3937708-----3863532-----3935456

cisco WS-C3750G-24T (PowerPC405) processor (revision E0) with 118784K/12280K bytes of memory.

Here are the values from a 6513:

SITSF-Central-Cat#sh mem

----------------Head---------Total(b)-------Used(b)------Free(b)-------Lowest(b)-----Largest(b)

Processor---44D06830---388962256----90744004---298218252---120559528---232898232

I/O--------------8000000----67108864----16487652----50621212-----50621212-----50619484

cisco WS-C6513 (R7000) processor (revision 1.0) with 458720K/65536K bytes of memory

[bruce.porter]

pop

memory free low-watermark - threshold is a security feature to protect the memory from DOS.

[michael.leblanc]

The 3750 shows the "lowest" amount of Processor memory available (presumably since last boot) as 43,916,928 bytes.

Perhaps if you monitor "free" and "lowest" Processor/IO memory over time, you can identify baseline values, then decide how much of a deviation would warrant notification.

The values will change as new features are brought online, and loads increase. So it will warrant periodic re-assessment.

Unfortunately, I think it is up to you to decide how low you wish to allow "free" memory to dip below your baseline before generating a notification.

I set my thresholds a couple MB lower than my baseline. If a notification occurs, I determine how low it went, and try to correlate it to a reason.

I'm doing what makes sense to me without guidance from anyone who might know better.

I'm not sure that there is a "right" answer.

That's all I can offer.

[bruce.porter]

www reference:

http://www.cisco.com/en/US/docs/ios/12_3t/12_3t4/feature/guide/gt_memnt.html

Guessing is the only way.

With 78MB of processor memory:

Router(config)# memory free low-watermark processor 10000

This sets the warning threshold to 10MB. i.e. 10%, sort of.

With 12MB of io memory:

Router(config)# memory free low-watermark io 1000

Sets the warning threshold for io to 1000. i.e. 10%

Out of 100MB total, keep a meg reserved for critical operations:

Router# memory reserved critical 1000

i.e. 1% @ 1MB.

memory reserve critical 1000

memory free low-watermark processor 10000

memory free low-watermark IO 1000