ubuntu 16.04 became VERY slow

[robert rottermann]

Hi there,

i am using ubuntu 16.04 on on a reasonably modern box.

During the last couple of weeks it has become unbearably slow.

Top shows

Tasks: 309 total,   1 running, 307 sleeping,   0 stopped,   1 zombie
%Cpu(s):  7.5 us,  1.9 sy,  0.0 ni, 90.6 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
KiB Mem :  8080208 total,   241524 free,  3555784 used,  4282900 buff/cache
KiB Swap:  8364028 total,  5313096 free,  3050932 used.  3080912 avail Mem

   PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND
  9947 robert    20   0 2941400 903600  78480 S  15.0 11.2 675:48.84 firefox
24504 robert    20   0 3149920 224720  15048 S  15.0  2.8 599:26.46 python2.7
  4246 robert    20   0  733312  92332  25724 S   2.3  1.1 202:24.89 skype

lscpu show the following:

robert at mozart:~/odoo_instances$ lscpu
Architecture:          x86_64
CPU op-mode(s):        32-bit, 64-bit
Byte Order:            Little Endian
CPU(s):                4
On-line CPU(s) list:   0-3
Thread(s) per core:    1
Core(s) per socket:    4
Socket(s):             1
NUMA node(s):          1
Vendor ID:             GenuineIntel
CPU family:            6
Model:                 42
Model name:            Intel(R) Core(TM) i5-2500 CPU @ 3.30GHz
Stepping:              7
CPU MHz:               2503.101
CPU max MHz:           3700.0000
CPU min MHz:           1600.0000
BogoMIPS:              6585.05
Virtualization:        VT-x
L1d cache:             32K
L1i cache:             32K
L2 cache:              256K
L3 cache:              6144K
NUMA node0 CPU(s):     0-3
Flags:                 fpu vme de pse tsc msr pae mce cx8 apic sep mtrr 
pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe 
syscall nx rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl 
xtopology nonstop_tsc aperfmperf eagerfpu pni pclmulqdq dtes64 monitor 
ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic 
popcnt tsc_deadline_timer aes xsave avx lahf_lm epb tpr_shadow vnmi 
flexpriority ept vpid xsaveopt dtherm ida arat pln pts

so what could be the reason for this behaviour?

how can I fix it?

thanks

robert