[Solved] Some sysctl values are lost after suspend/resume

[GJones]

Run 'system -w vm.dirty_bytes=5000000'

Suspend the system...

Resume, and vm.dirty_bytes is 0 again.

Put it in sysctl.conf, run 'sysctl -p', suspend and resume... Same thing.

Word is that this is a feature (no, I've no idea how) and will not be fixed. Given that, what is the least kludgy way to make Salix run 'sysctl -p' on resume?

[aurlaent]

You could create a hook in /etc/pm/sleep.d
https://wiki.archlinux.org/index.php/Pm ... _own_hooks
has some detailed info.

[GJones]

Thanks, that's what I was looking for!

Edit: to be fair this is still a kludge, since stuff not in sysctl.conf won't be applied. Even so, it helps.

[aurlaent]

Sure, but how often are you changing things like that on the fly?
(I guess I haven't found the power of these options)

[GJones]

Well, for starters vm.dirty_bytes is rather handy for preventing I/O starvation on desktops, at the expense of disk throughput. It can prevent those scenarios where some program is writing huge batches of stuff to the disk and other programs can't get a word in edgewise.

[GJones]

Okay, something is going wrong here. sysctl -p is running but the changes are being undone.

Code: Select all

/usr/lib/pm-utils/sleep.d/01grub resume suspend: success.
Running hook /etc/pm/sleep.d/00sysctl resume suspend:
vm.dirty_bytes = 5000000
...
# sysctl vm.dirty_bytes
vm.dirty_bytes = 0

00sysctl is properly set +x and looks like this:

Code: Select all

#!/bin/bash
case $1 in
   thaw)
      sysctl -p
      ;;
   resume)
      sysctl -p
      ;;
   *)
      ;;
esac


What am I doing wrong?

[GJones]

Hate to do this, but... bump?

[Shador]

Probably something else is running afterwards but I wouldn't know what. You could try this:

Code: Select all

grep -i sysctl /etc/pm/ /usr/lib64/pm-utils/ -r

Apparently this information is from a log:

Code: Select all

/usr/lib/pm-utils/sleep.d/01grub resume suspend: success.
Running hook /etc/pm/sleep.d/00sysctl resume suspend:
vm.dirty_bytes = 5000000
...
# sysctl vm.dirty_bytes
vm.dirty_bytes = 0

You could try to get some information from there what is resetting them. Possibly by increasing the verbosity.

[GJones]

The only invocation of sysctl I found was this:

Code: Select all

# grep -ir sysctl /usr/lib64/pm-utils/
/usr/lib64/pm-utils/sleep.d/99video:    sysctl -w kernel.acpi_video_flags=$acpi_flag


Which I'm pretty sure is not responsible.

[GJones]

N/M got it, it's /usr/lib64/pm-utils/power.d/laptop-mode (writing directly to /proc/sys/vm/dirty_ratio and whatnot). Overriding that via an empty /etc/pm/power.d/laptop-mode file works okay.