Memory & CPU
Your server has a limited amount of memory and processing power. When one stuck program takes most of it, everything else slows to a crawl — pages take ages to load and the database may be stopped to free memory.
- At a glance
- Group
- Resources
- Mellonbot
- Can fix it
- What it does
- Stops the runaway process safely.
- Approval
- Always with your OK
What you’ll notice
- 01Pages are very slow, or time out with “504 Gateway Timeout”
- 02The server feels sluggish when you log in
- 03Programs are stopped with “Out of memory” messages
- 04Your host warns about high CPU use
Why it usually happens
- 01A stuck or looping process, often PHP or a background job
- 02A sudden rush of visitors or bots
- 03Not enough memory for everything running on the server
- 04A plugin or app with a memory leak
Fix it yourself
How to fix it by hand
Comfortable with a terminal? Here’s what an experienced admin would do. Start with the read-only commands.
- 01
See what’s using the most CPU
The top lines are the busiest programs.
ps aux --sort=-%cpu | head -10 - 02
See what’s using the most memory
Compare this with the total in the next step.
ps aux --sort=-%mem | head -10 - 03
Check free memory
Look at the “available” column.
free -h - 04
Look for out-of-memory kills
Shows whether the system has been stopping programs to survive.
sudo journalctl -k | grep -i "out of memory" - 05
Restart the stuck service
Restarting the service is safer than killing single processes.
sudo systemctl restart 'php*-fpm'
With Mellonbot
How Mellonbot fixes it
- Checks CPU and memory use, and spots processes that have been stuck for a long time.
- Explains which program is using the power and whether that’s normal for your server.
- Offers to stop the runaway process safely, then checks your site is fast again.
- Remembers what’s normal for your server, so it can tell a real problem from a busy moment.
Not sure this is your problem? Ask us →
FAQ
Memory & CPU: common questions
Why is my website so slow all of a sudden?
Often one process is using all the CPU or memory. Checking the busiest processes on the server usually points straight to it.
What does “Out of memory: Killed process” mean?
The server ran out of memory and stopped a program — often the database — to keep itself running.
Still have a question?
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