Question for the caching experts... thanks... My device is running netSNMP 5.4.1 agent and has a fairly large private MIB. A client of ours runs an snmpwalk of the entire tree and is satisfied with the time it takes to dump all of the data.
Our tables use the default 10s cache value, and a few heavy-hitters take some time to complete the cache_load() operation due to the time it takes to gather data from the various hardware devices (e.g. - gathering lots of LED status over I2C and other busses). The customer, using a 20s timeout and a retry of 1 tells me he sees it takes about 1min 30 s to dump all of the data. The problem is.. he says that when he runs two simultaneous snmpwalks of the entire tree, the total time for the individual runs to complete jumps to 3-6 minutes and he has to raise the timeout to 60s. In addition, he saysif he runs three simultaneous walks, it can take HOURS to complete!!!!! (Don't ask why they do this, but they say they need to support this operation) I am just trying to figure out what might be the source of this extreme time increase. If I ponder the flow a bit, since the PDU processing is single threaded, it seems that handling an occasional request will cause a pause in sending the rsp, since the cache must be loaded every 10s or so. But once the cache is loaded, the rest of the table responses should be super fast. And even with a second request coming in for the same table from another source, this should not be a problem. The request may queue up behind another sources request that is causing a cache reload, but once that is done, this second sources rsp to the table should be lightning fast, served from the cache. My only thought is that somehow there is some cache thrashing going on between the cache handling and interaction with the incoming PDU requests. It almost seems like as the cells of a table are being responded to, the cache is being reloaded for each cell (or at least much more often than is needed). I need to study the cache handler code, and sorry for rambling, but I was wondering if anyone has experienced this problem when running multiple tree walks? Thanks, Randy Worzella ------------------------------------------------------------------------------ The modern datacenter depends on network connectivity to access resources and provide services. The best practices for maximizing a physical server's connectivity to a physical network are well understood - see how these rules translate into the virtual world? http://p.sf.net/sfu/oracle-sfdevnlfb _______________________________________________ Net-snmp-users mailing list [email protected] Please see the following page to unsubscribe or change other options: https://lists.sourceforge.net/lists/listinfo/net-snmp-users
