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.

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.

On Fr 24 Mai 2024 at 12:24, Woozy Song <suzyw0ng@outlook.com> wrote:

> 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.

I think ot is '-q b', the small letter b for the batch queue (a is for at).
The other letters are not used by default and just serve to indicate niceness.

'Andreas

--
ceterum censeo redmondinem esse delendam

In comp.os.linux.misc Woozy Song <suzyw0ng@outlook.com> 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.

An alternative to using at and batch (batch is what observes the load
limit by-the-way) is to install Task Spooler and use it for 'background
jobs'. You can tell it to run jobs sequentially, or max X in parallel
(you get to pick X).

https://viric.name/soft/ts/

You can also submit jobs that "depend upon" other jobs, so that the
dependent job won't run until the "parent" completes successfully.