There are various tools in the market (some are free) for monitoring server memory stats for UNIX boxes.
However, if you want load runner to capture the stats, there are load runner native monitors available for that.
Go to the UNIX box and vi the inetd.conf file and remove the # entry before rpc.rstatd in the file to enable the daemon service. Now, restart the controller m/c once. After the Controller has been started go to run window in the LR Controller and open the UNIX monitor and add the server to monitor. Now add the suitable counters to monitor. Monitoring should start immediately. Go to Load runner monitor ref for more details.
You have to use the counters like Paging rate (<50), pagein/sec, pageout/sec, %used (<80%) counters and as leobor has suggested, HP Performance monitor best practice document should give you more light.