imperfect clearing of memory cache

[Impavidus]

It seems your unreclaimable slab is excessively large. For comparison on my computer:

$ cat /proc/meminfo
MemTotal:        8105308 kB
MemFree:         3333608 kB
MemAvailable:    4583560 kB
Buffers:          166308 kB
Cached:          1767816 kB
(...)
Slab:             147812 kB
SReclaimable:     108240 kB
SUnreclaim:        39572 kB
(...)

Slab is for in-kernel data structures. As I said, I don't know the details of memory management. Do you, by any chance, use a non-standard kernel? Although you quoted 4.4.0-101-generic, which seems to be the standard on 16.04 and 14.04 with HWE. I imagine there might be a small memory leak in the kernel (but that should have been discovered) or some driver, but I don't feel capable providing more help with that.

And any particular reason to keep your computer running very slowly for a couple of days more instead of a simple reboot?

[photonxp]

root@mirzman-workstation:~# ps --sort -rss -eo pid,pmem,rss,vsz,comm | head -20
  PID %MEM   RSS    VSZ COMMAND
 7392  5.7 939048 2968784 Web Content
 7164  4.4 720768 3052668 Web Content
 7121  4.3 713492 2926076 Web Content
... ...

What is "Web Content" here? Do you use it a lot or just occasionally? What is it running for?
You can try killing "Web Content" and then run again the command:

free && sync && sudo sh -c "echo 3 > /proc/sys/vm/drop_caches" && free

You can run this command as non-root user then enter the password for root when it's required.

[vasa1]

What is "Web Content" here? ...

It originates from Firefox.

[mirzman]

It died
I tried echo 10000000 >/proc/sys/vm/min_free_kbytes
The result will be several days later

[mirzman]

Do you, by any chance, use a non-standard kernel? Although you quoted 4.4.0-101-generic, which seems to be the standard on 16.04 and 14.04 with HWE. I imagine there might be a small memory leak in the kernel (but that should have been discovered) or some driver, but I don't feel capable providing more help with that.

And any particular reason to keep your computer running very slowly for a couple of days more instead of a simple reboot?

Yes, I use standard software.
It's no reason, but my uptimes used to be 60 days several months ago, and restarting system every 3 days is something terrible for me now...

[mirzman]

What is "Web Content" here? Do you use it a lot or just occasionally? What is it running for?
You can try killing "Web Content" and then run again the command:

free && sync && sudo sh -c "echo 3 > /proc/sys/vm/drop_caches" && free

You can run this command as non-root user then enter the password for root when it's required.

It's firefox. I'll try this several days later when enough amount of memory will leak.

[mirzman]

It died
I tried echo 10000000 >/proc/sys/vm/min_free_kbytes
The result will be several days later

System went to swap immediately... This don't work.

root@mirzman-workstation:~# uptime
 14:04:08 up 56 min,  1 user,  load average: 2,39, 1,60, 1,19
root@mirzman-workstation:~# cat /proc/sys/vm/min_free_kbytes
10000000
root@mirzman-workstation:~# free && sync && echo 3 > /proc/sys/vm/drop_caches && free
              total        used        free      shared  buff/cache   available
Mem:       16294664     1281416    14197052      429076      816196     1846350
Swap:      16636924     1257740    15379184
              total        used        free      shared  buff/cache   available
Mem:       16294664     1281576    14205440      428680      807648     1850532
Swap:      16636924     1257612    15379312

[mirzman]

You can try killing "Web Content" and then run again the command:

free && sync && sudo sh -c "echo 3 > /proc/sys/vm/drop_caches" && free

You can run this command as non-root user then enter the password for root when it's required.

It don't help...

root@mirzman-workstation:~# free && sync && sudo sh -c "echo 3 > /proc/sys/vm/drop_caches" && free
              total        used        free      shared  buff/cache   available
Mem:       16294664     4663356      432936      597716    11198372     1134764
Swap:      16636924      576192    16060732
              total        used        free      shared  buff/cache   available
Mem:       16294664     4664364     1172776      578144    10457524     1206540
Swap:      16636924      576192    16060732

root@mirzman-workstation:~# killall -9 firefox

root@mirzman-workstation:~# ps --sort -rss -eo pid,pmem,rss,vsz,comm | awk '{sum+=$3}END{print sum}'
2886740

root@mirzman-workstation:~# ps --sort -rss -eo pid,pmem,rss,vsz,comm | head -20
  PID %MEM   RSS    VSZ COMMAND
 2092  1.9 321712 3001048 Telegram
22052  1.8 302164 2490956 chromium-browse
19246  1.7 285720 2376336 thunderbird
21898  1.3 225412 3171484 chromium-browse
 1037  0.8 134940 626540 Xorg
 2235  0.6 109484 1249884 compiz
 2113  0.5 87680 767204 gnome-system-mo
22034  0.5 85752 1118964 chromium-browse
 8157  0.5 83064 1714332 chromium-browse
 1892  0.4 66880 1305000 nautilus
 1888  0.3 64620 1367316 gnome-software
 2130  0.3 53492 724940 gnome-terminal-
23510  0.3 53184 1723176 chromium-browse
23980  0.2 46448 1699960 chromium-browse
22249  0.2 37656 2191820 chromium-browse
 1726  0.2 35264 736964 hud-service
10018  0.2 32860 1143852 gedit
 4645  0.1 31044 1650392 chromium-browse
22243  0.1 30928 2104872 chromium-browse

root@mirzman-workstation:~# free && sync && sudo sh -c "echo 3 > /proc/sys/vm/drop_caches" && free
              total        used        free      shared  buff/cache   available
Mem:       16294664     1958312     3720052      571324    10616300     3918284
Swap:      16636924      535036    16101888
              total        used        free      shared  buff/cache   available
Mem:       16294664     1954044     3958448      571028    10382172     3923780
Swap:      16636924      535032    16101892