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CSS-11500 Memory resource indication


We are having css11500 with three slots and only one slot is used. It shows memory installed as 256 mb and used 128 mb. This is with minimum load. Is is not objectionable to see 50 % of memory used at no-load condition. In production environment there will be at least 600 connections establishing via load balancer. What can be done if memory utilization goes very high ?

Thankx in advance


Cisco Employee

Re: CSS-11500 Memory resource indication


You should not be that concer about the memory but about the CPU utilization and Flows Allocated.

Look at this from from my CSS:

CSS01(debug)# show system-resources ${output}

System Resources for 1/1:

Installed Memory: 268,435,456 (256 MB)

Free Memory: 137,467,104 (131 MB)

CPU: 23%

The output above shows resources for the SCM, notice the usage is around 50%. The memory that you see there is just normal cause this include the operating system loaded.

System Resources for 2/1:

Installed Memory:

134,217,728 (128 MB)

Free Memory: 29,121,376 (27 MB)

CPU: 0%

This other output is from the IOM module, that is what seems to be low.

It is normal for the amount of free/allocated memory to remain relatively stable on the CSS. In general memory for buffers, Flow Control Blocks (FCBs) is pre-allocated at initialization time.

The only dymanic memory allocation in general when the system is up and running is for keepalives, content replication and any new configured rules, etc.

This is a normal numbers due to the fact that the memory that is free is not allocated, and number like the flow statistics reflects better what is your real capacity, because you will see the amount of free flows, and the amount of allocated flows.

Each module will allocate a certain amount of memory at boot time for flows.

Depending if the module has 128 or 256 less or more memory is available at boot time for flows.

Every module will begin using free memory when the all the boot allocated memory is used for flows. This will happen until there is 4MB of free memory left on the module. When this happens, no more flows can be setup.

The SCM is a little different in that memory is for switch management as well so it is capable of handling slightly less flows."

In other words the CSS when booting up assigns the memery for FCB's and only when that memory is used the Free Memory of the outputs above will be used, so you need to be be concern about this:

Flow Manager Statistics - Slot 1, Subslot 1:

Number of Allocated Flows (non-purged) 4

Number of Free Flows 65532

Number of Allocated fast-path FCBs 4

Number of Free fast-path FCBs 131068

Number of Flow Drops 0

Max Number of Flow Control Blocks 537488

Flow Manager Statistics - Slot 2, Subslot 1:

Number of Allocated Flows (non-purged) 11

Number of Free Flows 113237

Number of Allocated fast-path FCBs 11

Number of Free fast-path FCBs 131062

Number of Flow Drops 0

Max Number of Flow Control Blocks 202590

Notice that the number of Free fast-path FCBs is very high on both modules,

almost no use. Everything seems to be fine.

This outputs were taken from one of my CSS that is getting no flows at all.

Hope it helps!!