Not so long ago dramatically increased the load on the site to the stage... nothing works, only intensive feeding resources.
The atop utility allows you to save logs that contain different server metrics. Very useful for diagnosing performance problems. Works interactively and in the background.
apt-get install atop
For startup enough:
service atop start
By default saving every 10 minutes, this value can be changed in the file /etc/default/stop or /etc/sysconfig/atop (variable INTERVAL).
By default, logs are stored in the directory /var/log/atop, file naming is done in the format atop-YYYYMMDD.
atop -r /var/log/atop/atop_20190101
m - build processes on occupied memory;
d - build disk usage processes;
n - build processes to use the network (available only with the patch installed);
v - shows more detailed information about the processes (user, date and time of the process start);
u - build a table by the most voracious user
i - change check time, default 10 seconds;
g - will return everything to default output;
t - move to the next time interval;
Shift + t - move to the previous time interval;
Shift + m - sort processes by resident memory;
Shift + C - sort processes by CPU consumption (default);
Shift + d - sort processes by disk usage;
Shift + n - sort processes by network usage;