3 ms·
My rule of thumb is that the end users of a web application will perceive that the system is "slow" if the 1 minute load average is above 4 on the application o
by geoffc 17y ago
My rule of thumb is that the end users of a web application will perceive that the system is "slow" if the 1 minute load average is above 4 on the application or database server.
- seiji 17y agoHuh? What if I have a 48 core AMD server? A fully CPU-bound load average of 48 would be great. Load average can tell you if the system is under-used, but it can't tell you how the system is over-used. I regularly have a few dual core systems spike to load averages of 50+ because of suboptimal NFS mounts. The NFS issue keeps processes waiting around with nothing to do for a while. Those processes are still counted towards the "load" even though they have no CPU activity (they are blocked on IO).
- geoffc 17y agoAgreed it is not accurate for huge servers and IO bound cases but I have found it to be a good rule of thumb for a LAMP web application stack on anything from single to 8 core machines. It is a useful metric to start digging deeper into the machine.
- spudlyo 17y agoThe Linux kernel also checks to see if there are any tasks in a short-term sleep state called TASK_UNINTERRUPTIBLE. If there are, they are also included in the load average sample. Shown in top as being in the 'D' state.
- FlorinAndrei 17y agoAlways divide the load average by the number of cores. Maybe we should re-define load average, as the old definition divided by the number of cores.