RSA Authentication Manager shows high memory utilization when running top or vmstat and some SNMP traps
Originally Published: 2010-03-23
Article Number
Applies To
RSA Product/Service Type: Authentication Manager
RSA Version/Condition: 7.1 SP4/3.0, 8.x
Issue
- RSA Authentication Manager 7.1 SP4 and RSA SecurID Appliance 3.0.4 show low free memory, with either the top or vmstat command.
- Some SNMP traps for high memory utilization are being triggered even when the system is idle. This affects both Dell and Intel hardware appliances as well as virtual machines.
- Free memory displayed with vmstat consistently reading low at between 95-100mb at all times, even when system is not under load:
procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu---- r b swpd free buff cache si so bi bo in cs us sy id wa 2 0 20512 219480 64864 1275756 0 0 1 19 18 3 8 6 86 0
- SNMP traps set to trigger against either top and vmstat are sending a false positive for memory shortfall. It would appear free mem is below a critical level of 5-10% available when using vmstat or top. In fact, this is in reality a false positive alert.
Cause
The RSA SecuriD Appliance 3.0 is an rPath Linux kernel. This particular version of Linux uses a memory management known as "lazy man" memory mapping.
In such a memory management/kernel approach, (scroll to the second to the last paragraph of the page on this link):
To make the most efficient use of real memory, Linux automatically uses all free RAM for buffer cache, but also automatically makes the cache smaller when programs need more memory.
Resolution
[root@cs-appliance3-05 ~]# free total used free shared buffers cached Mem: 3369872 3149532 220340 0 64864 1277488 -/+ buffers/cache: 1807180 1562692 Swap: 8241336 20512 8220824Reading the -/+ buffers/cache field indicate in this instance of the older RSA SecuriD Appliance 3.0, that approximately 1.5 GB are free for re-allocation when system load increases; more than enough free memory.
On the same model Dell appliance updated to Authentication Manager 8.1 with SUSE Linux, we still see almost .7G available.
On the model with 8G of RAM, we see 3.6 GB of RAM available for reallocation when needed.
You can also use an SNMP OID for the trap vs free output. For more information on SNMP traps on Linux, reference this article on Linux SNMP OIDs for CPU,Memory and Disk Statistics.
You should consider the use of the UCD OID .1.3.6.1.4.1.2021 for CPU and memory usage versus using HOST MIBs, noting all reported available thresholds report in kilobytes.
Authentication Manager 8.1 SNMP OIDs
- Total physical memory for the operating system memory in KB: .1.3.6.1.4.1.674.10892.1.400.20.1.5
- Available physical memory for the operating system memory in KB.: .1.3.6.1.4.1.674.10892.1.400.20.1.6
Complete list of UCD MIB OIDS for older RSA SecurID Appliance 3.0
| Description | OID |
| Total Swap Size | 1.3.6.1.4.1.2021.4.3.0 |
| Available Swap Space | 1.3.6.1.4.1.2021.4.4.0 |
| Total RAM in Machine | 1.3.6.1.4.1.2021.4.5.0 |
| Available Real Memory | 1.3.6.1.4.1.2021.4.6.0 |
| Total RAM Free | 1.3.6.1.4.1.2021.4.11.0 |
| Total RAM Shared | 1.3.6.1.4.1.2021.4.13.0 |
| Total RAM Buffered | 1.3.6.1.4.1.2021.4.14.0 |
| Total Cached Memory | 1.3.6.1.4.1.2021.4.15.0 |
Workaround
Notes
