Swapiness not changing after reboot

0xA1B2 · June 5, 2020, 8:12am

Hello,

I try to set swapiness to 0 but it goes back to 10 after a reboot.

cat /proc/sys/vm/swappiness
10

sudo gedit /etc/sysctl.conf

With Spaces around “=”
Add:

vm.swappiness = 0

save, reboot

cat /proc/sys/vm/swappiness
10

I tried a different path/file (sudo gedit /usr/lib/sysctl.d/swap.conf), but same issue, the swapiness value is either not set to 0 or overridden back to 10 by something else.

miguelinux · June 5, 2020, 2:43pm

clr-power-tweaks is setting /proc/sys/vm/swappiness

github.com

clearlinux/clr-power-tweaks/blob/deda22de2d01598f587e55f095f570d735acc936/src/data.h#L51


      
          struct write_struct write_list[] = {
          	// synchronous dirty ratio --> 50%
          	{"/proc/sys/vm/dirty_ratio", "50", 0},
          	{"/proc/sys/kernel/unprivileged_bpf_disabled", "1", 0},
          
          
	// start IO at 5% not 10%... start IO a little earlier asynchronously, since memory sizes are bigger now
          	{"/proc/sys/vm/dirty_background_ratio", "5", 0},
          
          
	// 15 seconds before the VM starts writeback, allowing the FS to deal with this better
          	{"/proc/sys/vm/dirty_writeback_centisecs", "1500", 0},
          	{"/proc/sys/vm/swappiness", "10", 0},
          	{"/sys/kernel/mm/transparent_hugepage/khugepaged/scan_sleep_millisecs", "30000"},
          	{"/sys/devices/virtual/graphics/fbcon/cursor_blink", "0", 0},
          	{"/sys/kernel/rcu_expedited", "0", 0},
          	{"/proc/sys/vm/mmap_min_addr", "65536", 0},
          
          
	// oom less
          	{"/proc/sys/vm/extfrag_threshold", "100", 0},
          	{"/sys/kernel/mm/ksm/sleep_millisecs", "4000", 0},
          
          
	// w /sys/kernel/mm/ksm/run - - - - 1

puneetse · June 5, 2020, 3:10pm

See man clr-power-tweaks.conf for how to configure clr-power-tweaks to your liking.

daja · June 5, 2020, 4:37pm

Absolutely, this does the job

sudo echo ”/proc/sys/vm/swappiness 0“ > /etc/clr-power-tweaks.conf

ahkok · June 5, 2020, 5:00pm

That is almost correct, you want to do something like this:
echo ”/proc/sys/vm/swappiness 0“ | sudo tee -a /etc/clr-power-tweaks.conf

ohmyfish · June 5, 2020, 5:08pm

sry, this is news to me - is the following example (another override) correct :

echo ”/sys/devices/system/cpu/cpu*/cpufreq/scaling_governor powersave“ | sudo tee -a /etc/clr-power-tweaks.conf

(
until schedutil & if the computer has heavy work to perform, a manual/temporary switch per:

echo performance | sudo tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
)

daja · June 5, 2020, 5:17pm

You’re right. I wrote the cmd as root, my bad … and I add the sudo cmd here

inmanturbo · June 5, 2020, 5:22pm

Well,

appends to the file if indeed it already exists.

This would destroy then create it anew with just the one line.

daja · June 5, 2020, 5:44pm

Not really
sudo echo … > /path/to/file does nothing, because the sudo cmd doesn’t give privilege for the redirection > only for the echo
But you’re right, the > overwrite any existing file.

inmanturbo · June 5, 2020, 5:49pm

err yeah, that’s one strong echo… that too

ahkok · June 5, 2020, 5:52pm

My personal preference isn’t to use tee, but just sudo vi ... instead and edit the file in place, add a little comment if needed etc. it’s not copy-paste easy, but worth the time to see a previous version and perhaps some hints I left myself earlier.

ohmyfish · June 5, 2020, 8:03pm

no answer, but -

printf "/sys/devices/system/cpu/cpu*/cpufreq/scaling_governor powersave" | sudo tee --append /etc/clr-power-tweaks.conf

works for me. &

printf '\n%s\n' "/proc/sys/vm/swappiness 5" | sudo tee --append /etc/clr-power-tweaks.conf

after that + earlyoom (now).

chesterlug · June 9, 2020, 4:31pm

Why enable powersave ?