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From: Woozy Song <suzyw0ng@outlook.com>
Newsgroups: comp.os.linux.misc,alt.os.linux
Subject: Re: setting load limit for atd batch system?
Date: Fri, 24 May 2024 12:24:05 +0800
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Woozy Song wrote:
> So the atd supposedly will not start another job until load factor falls 
> below a limit. Different documentation gives the default as 0.8 or 1.5
> Now I launch a job that uses 4 cores on a 6-core CPU. If I run top 
> command, I see four processes running close to 100%.
> Now if I submit another job 10 seconds later, that starts thereby 
> overloading the CPU. Documentation suggests setting load limit to more 
> than n-1 for n CPU cores, but I think that is intended for single-thread 
> jobs. I have tried altering the load limit in atd.service file to all 
> sorts of values, but second job keeps starting while the first is 
> flogging the CPU. I check with 'ps -ef|grep atd' to see it is using the 
> desired load limit. I am aware that the load factor is an average, you 
> can see it changes slowly in top/htop/glances. So I also increase the 
> delay between jobs to 30 seconds, but still nothing works. So it looks 
> like I have to specify a time like 'now+60 minutes' when I submit, 
> requiring some guess how long first job runs. I know I can install a 
> proper job scheduler such as Some Grid Engine, but that is more work.
> This is on Debian 11, by the way.

I found the trick: you have to add '-q B' to command, then load-limit 
rule applies (it behaves like batch command instead of at). Otherwise it 
uses default queue 'a' that only uses time without load limit.