Linux – Performance monitoring from guest OS

There are a couple lines in your php.ini file that are relevant. One is the memory_limit which defines how much RAM any given php script is allowed to eat through, the other is max_execution_time which defines how much CPU time it gets before being killed off. Be aware that this latter time is based on CPU time not clock time, so if it isn't using any CPU it might not ever add up.

Also as you noted these are temporary hacks to mitigate a mis-behaving app, not a real fix. You might find strace useful to figure out exactly what the memory-hogging processes are up to.

Looking at basic system metrics does not give a good indication of performance. It can indicate how performance is constrained - but if you want to measure the performance of your applications then you really need to look at real transactions.

Regardless, there are no end of tools for measuring performance. I use nagios. It's a bit lacking in trending / capacity management but is amazingly flexibile in reporting, escalation, fault isolation and to add custom scripts (which you'll need if you want to measure your transacions). Certainly there are probes available to cover all the metrics you've listed for both MSWindows and Linux.