I am currently hosting a test website under a 8 vcpu and 2gb ram virtual machine using nginx and php-fpm, the host machine is hosting other virtual machines doing the same thing with 10gbps network interface. During my stress test after 50 users requesting concurrently my test website’s response time rises from 800-900ms on normal to around 2 seconds. After this test I tried to increase the virtual machine’s ram to 6gb but there were no change in the response time at all. What could be causing this?
Oooh the list is kind of endless
- Poor application design
- Poor database queries.
- Poor choice of database engine.
- Poor nginx tuning.
- Poor php tuning.
- Insufficient memory
So with the information you provided it could literally be anything.
Go away, look at your system using tools like top, vmstat, iostat, sar, free etc. Perhaps even consider a full monitoring solutin Watch what happens to the system resources see which ones are being consumed and take appropriate actions. Rinse and repeat.
It really is science, not lick your finger and hold it in the air stuff. Bring scientific method to bear, don’t scream HALP ! at the internet and expect it to guess whats wrong.