Developers who want to understand how their programs use the cache for read and write operations might also want to monitor the cache.
Data requested by an application is mapped to the cache and then copied from there.
However, when there is not enough memory to create an effective cache, the system must retrieve more data from disk, resulting in I/O operations that can impact overall performance.
Such a shortage of cache space can be considered a cache bottleneck.
in seconds) for which the data in this particular cache entry will remain valid." ::= ns Cache Status OBJECT-TYPE SYNTAX Netsnmp Cache Status MAX-ACCESS read-write STATUS current DESCRIPTION "The current status of this particular cache entry.
Acceptable values for Set requests are 'enabled(1)', 'disabled(2)' or 'empty(3)' (to clear all cached data).
From my experience I know that it’s pretty common in all kinds of network equipment as switches, routers etc, to update SNMP agent counters (OID’s) in real time.
The first row of the table holds the “cache timeout” (15 seconds) of the interfaces table (if Table – 22.214.171.124.126.96.36.199).
Cache object counters provide information about data hits and misses and about file I/O operations that reflect how efficiently their applications access data in the file system cache.
However, because the cache counters are based on the views mapped by the Cache Manager and not on data from the Virtual Memory Manager, the cache counter values do not provide definitive information about bottlenecks.
The FC_RTGraph screenshot below (one application of the FCMS suite) shows the result of the eth0 interface being polled every second.
It depends of course on whether a 15 seconds update interval suits your needs but in my case it did not and I decided to start “googling” for a way to modify this behavior. The contains a table called “ns Cache Table (188.8.131.52.4.1.8072.1.5.3) which contains entries describing, quoting from the mib, “The length of time (in seconds) for which the data in this particular cache entry will remain valid”.
In some cases, cache counters can report low rates of hits or high rates of misses, suggesting that the system is accessing the disk when, in fact, the requested data has been retrieved from memory.