Scanner Priority set to -20 but running at regular nice level

[audiomuze]

> This can't work, since the unprivileged user LMS runs as can only choose
> a lower priority

Which means we should probably remove it from LMS?...

[audiomuze]

Scanner Priority set to -20 but running at regular nice level

Scanner Priority is set to -20 and rescans initiated by LMS are with --priority=-20, however looking at the scanner.pl process using HTOP it's running at 20? Should scanner.pl's priority no be -20 when set accordingly in LMS?

[Paul Webster]

I have never tried it ... but set it to 10 and -10 to see if it shows that the number is being used etc

[audiomuze]

I have never tried it ... but set it to 10 and -10 to see if it shows that the number is being used etc

It's been years since I was a frequent user of LMS so a little rusty coming back, but I seem to recall it would actually run at the priority set, which it doesn't appear to be doing now.. I'm manually changing the priority outside of LMS and the rescan definitely seems to run faster when that's done.

[mherger]

Scanner Priority set to -20 butrunning at regular nice level

LMS is using the "setpriority" system call on unixy system. I couldn't
find any special handling of the value whatsoever. I assume you're on Linux?

[Roland0]

This can't work, since the unprivileged user LMS runs as can only choose a lower priority
simple solution: set priority in service unit / init script
better solution: add CAP_SYS_NICE capability in service unit / init script (or set LimitNICE instead)

[audiomuze]

LMS is using the "setpriority" system call on unixy system. I couldn't
find any special handling of the value whatsoever. I assume you're on Linux?

LMS on Linux, yes.

This can't work, since the unprivileged user LMS runs as can only choose a lower priority
simple solution: set priority in service unit / init script
better solution: add CAP_SYS_NICE capability in service unit / init script (or set LimitNICE instead)

It used to work years ago, perhaps something in the code has changed or my permissions in this instance are different from what a default distro based install would be. I'm in essence just unpacking the odd nightly to update my install.

> This can't work, since the unprivileged user LMS runs as can only choose
> a lower priority

Which means we should probably remove it from LMS?...

Please don't, it'd be better to implement a fix. For large libraries being able to run scanner.pl at -20 is essential to avoid lengthy update scans.

[Roland0]

> This can't work, since the unprivileged user LMS runs as can only choose
> a lower priority

Which means we should probably remove it from LMS?...

Not necessarily, as mentioned modifying the service unit / init script should fix this
systemd (not tested, as I don't use it):
- set LimitNICE (preferred)
- or set CAP_SYS_NICE capability (potential security implications)

non-systemd distros eg. Devuan:
- config in /etc/security/limits.d/
- start-stop-daemon --capabilities option

Please don't, it'd be better to implement a fix. For large libraries being able to run scanner.pl at -20 is essential to avoid lengthy update scans.

You can simply modify the service unit to include

Nice=
CPUSchedulingPolicy=
CPUSchedulingPriority=
IOSchedulingClass=
IOSchedulingPriority=

[audiomuze]

You can simply modify the service unit to include

Nice=
CPUSchedulingPolicy=
CPUSchedulingPriority=
IOSchedulingClass=
IOSchedulingPriority=

Would that not cause LMS to run at highest priority, rather than only scanner.pl when invoked?

[Roland0]

Would that not cause LMS to run at highest priority, rather than only scanner.pl when invoked?

Yes. Exact behavior may depend on LMS spawning the external scanner or using the internal one.
Or use LimitNICE / capabilities

[mherger]

Please don't, it'd be better to implement a fix. For large libraries being able to run scanner.pl at -20 is essential to avoid lengthy update scans.

What kind of hardware are you running your LMS on. In my experience I found the scanner to be mostly I/O bound, not CPU.

[audiomuze]

What kind of hardware are you running your LMS on. In my experience I found the scanner to be mostly I/O bound, not CPU.

i5-7600T, Arch Linux, 2x local SATA3 drives, 16GB RAM. I've always found scan to run faster if set to -20. In years gone by it used to run as highest priority without requiring intervention.