Configuring Memory Settings
Configuring memory can help tune application performance. Two types of memory are provided: object cache and wired process memory. If wired process memory is exhausted, the processes use unwired memory.
See the following topics for more information on these memory types:
Object Cache
Object cache is shared memory. Both the size of the forwarding database and the size of the policy database are taken from object cache. Therefore, the size of object cache must be more than the sum of the sizes of both of these databases.
To configure object cache, specify a value that is a multiple of 128 MB and up to 512 MB for the Multiservices 100 PIC or up to 1280 MB for the Multiservices 400 PIC. However, if you set wired process memory as well, the maximum value for the object cache on the Multiservices 100 PIC is 128 MB and 768 MB on the Multiservices 400 PIC.
The current recommendations when configuring memory settings Multiservices PICs are as follows:
- Do not exceed a policy database size of 64 MB.
- Stay with one rule per term.
- Keep the object cache size high (1280 MB on Multiservices 400 PICs and DPCs and 512 MB on Multiservices 100 PICs).
- Do not configure anything for forwarding database.
- Keep the number of service sets per Multiservices PIC below 1000.
 | Note: When the extension-provider statement is first configured, the PIC reboots. Changing the object cache size, the policy database size, or the forwarding database size on a running system causes the PIC to reboot. |
Wired Process Memory
Wired process memory, or Big TLB, is memory used by the operating system that is pretty much "off limits" to another application. If wired process memory is exhausted, the processes use unwired memory.
The size of wired process memory is configurable. To reserve Big TLB, configure the wired-process-mem-size statement at the [edit adaptive-services service-package extension-provider] hierarchy level.
| Note: When the wired-process-mem-size statement is first changed, the PIC reboots. |
As of Junos OS Release 11.2, the number of processes supported by Big TLB is also configurable. When you configure multiple Big-TLB-supported processes, the physical memory is divided equally among the number of processes that use it. For example, if mem-size is 1024 MB and the number of processes (num-procs) supported is 8, then each process is allocated 128 MB of physical memory. Thus, the amount of physical memory that is allocated to each process is mem-size/num-procs.
To specify the number of processes that use Big TLB, use the wired-max-processes statement at the [edit adaptive-services service-package extension-provider] hierarchy level. The amount of memory that can be reserved for Big TLB is platform dependent.
The amount of object cache is also dependent on the amount of wired memory. The following table lists details per platform.
Table 1: Wired Memory and Object Cache Combinations in Multiservices PICs
Device | Max. Object Cache (MB) | Max. Wired Memory (MB) | Max. Number of Processes |
|---|---|---|---|
Multiservices 100 PIC | 512 | 0 | 0 |
0 | 512 | 8 | |
Multiservices 400 PIC Multiservices 500 PIC Multiservices DPC | 1280 | 0 | 0 |
256 | 1024 | 8 |
