A technique for scheduling tasks to be run at a specific time or on a specific event.
22
votes
1answer
1k views
High CPU usage with CFS?
I asked a previous question to try and isolate the source of an increase in CPU usage when moving an application from RHEL 5 to RHEL 6. The analysis that I did for that seems to indicate that it is ...
20
votes
7answers
18k views
Where are cron errors logged?
If I setup cron jobs incorrectly they appear to silently fail. Where should I look for an error log to understand what went wrong?
11
votes
2answers
511 views
What is a simple way to schedule a single event to happen at some time in the future?
There are often times that I want my computer to do a single task, but not right now. For example, I could have it notify me in 30 minutes that it is time to leave work. Or maybe I want it to run a ...
10
votes
2answers
235 views
What are the effects, if any, of scheduler priorities and policies for threads in an uncontended cpuset?
I have a Linux system where we have used cgroups to create two cpu_exclusive cpusets, A and B, and where we have migrated all user threads and all unbound kernel threads to a cgroup attached to cpuset ...
8
votes
2answers
535 views
how to queue a command to run after another command finishes?
Sometimes I start a program that takes a very long time to finish (emerge), then realize that I should go to bed instead of waiting for it. If I know this in the first place I would run
program; halt
...
8
votes
1answer
2k views
Isolating cause of higher CPU usage on RHEL 6 vs RHEL 5
I'm currently looking to move our system from RHEL 5 to RHEL 6, but I've run into a snag with unexpectedly high CPU usage on the RHEL 6 machines. It appears that this may be due at least in some part ...
7
votes
1answer
328 views
Why can a system become unresponsive?
I just executed dot (a program for drawing directed graphs) with an input file that was so big that it couldn't be rendered in a reasonable amount of time.
My whole system froze. I could barely make ...
7
votes
1answer
150 views
Prioritise X applications with focus
Is there a way to prioritise X applications with focus, preferably both in terms of CPU and I/O?
Something like all X applications are niced and ioniced down in priority, but when they gain focus ...
6
votes
2answers
3k views
Bash Script on Startup? (Linux)
Is there any way to make/run a bash script on reboot
(like in Debian/Ubuntu for instance, since thats what my 2 boxes at home have)
Also, any recommended guides for doing cron jobs? I'm completely ...
6
votes
4answers
404 views
Scheduling commands by system inactivity
So cron or at can schedule our commands to run at the exact time we need them to, but can we schedule commands to run when systems are inactive?
Something like:
echo "some_commands" | when 'cpu ...
6
votes
2answers
9k views
How can get a list of all scheduled cron jobs on my machine?
My sysadmin has set up a bunch of cron jobs on my machine. I'd like to know exactly what is scheduled for what time. How can I get that list?
6
votes
3answers
962 views
Which Scheduling algorithm is used in Linux?
Recently in an interview I was asked about the Scheduling algorithm used by Linux Operating system. What is the algorithm used any why?
Also, what algorithm is used in in real-time operating systems ...
6
votes
1answer
206 views
Why mkfifo behaves like a LIFO?
If i do.
mkfifo /tmp/a
echo 'one'>/tmp/a
in the while from another terminal
echo 'two'>/tmp/a
and from a third terminal
more /tmp/a
Why i obtain as output of the last command this?
...
5
votes
1answer
1k views
How can you schedule a computer to boot at a specific time?
Usually BIOSes have an option to schedule a time to which to boot at. Is there a Unix/Linux interface to specify the scheduled boot?
5
votes
2answers
426 views
Does Linux kernel 3.x use the CFS process scheduler?
Does the latest version of the Linux kernel (3.x) still use the Completely Fair Scheduler (CFS) for process scheduling which was introduced in 2.6.x ?
If it doesn't, which one does it use, and how ...
5
votes
1answer
357 views
Linux process scheduling - Cap/Weight based?
I am just trying to understand the basics of Linux scheduler.
Is Linux scheduler a Cap based or weight based scheduler?
I was previously using Xen. Now I am moving from Xen to KVM. I read VMs are ...
4
votes
4answers
276 views
How to prevent atd from running past jobs?
The at daemon is a great tool! However, if a job is scheduled for 8:00 am and the machine is off at that time, at will run the job whenever the machine is booted. What I would like to do is stop it ...
4
votes
1answer
759 views
How do I view the IO priority of a process?
How can I view the IO priority of a process? like to see for example if something has been ionice-ed.
4
votes
2answers
259 views
Simple queuing system?
Given a commodity PC, we would like to use it to execute some tasks in the background round the clock.
Basically, we would like to have commands like:
add-task *insert command here*
list-tasks
...
4
votes
1answer
206 views
Are there any Workload Management subsystems for Linux?
Asked this on superuser, got no response:
Can anyone tell me of the status/state of WLM (Workload Management) kernel scheduler systems in Linux? Alternatively, any user-space process goal-based load ...
3
votes
2answers
446 views
How does a script/program executes in unix?
I have a doubt about the execution pattern of a unix script.
For example a script containing lines:
command B
function C()
{
Myscript // Myscript is a script
command D
}
command E
and ...
3
votes
2answers
269 views
How do I execute a script later?
I need to compile gcc45 on my computer and that's a lengthy and resource-intensive process for my computer, so I'd prefer to have it do it while I sleep (at night).
What's the closest thing to:
$ ...
3
votes
2answers
970 views
Add a one-off scheduled task through a shell script?
I'd like to execute a task at a given time, once.
I know I can just use crontab -e to add it there, but I'd like to do that through a shellscript. crontab -e gives me some temporary file to edit ...
3
votes
2answers
245 views
How preemption works on Linux when a program has a timer less then 4ms?
Jiffies in most Linux system are defaulted to 250 (4ms). The questions is that what happens when a program has a usleep() less then 4ms ? Of course it works as should when it is scheduled. But what ...
3
votes
3answers
153 views
Changing the disk scheduler on the fly
Can the Linux disk scheduler be changed on the fly by writing to /sys/block/sda/queue/scheduler? Should applications (e.g. Mysql) be stopped / started when changing?
3
votes
3answers
205 views
GNU: Delayed jobs Queue
Is there a simple way for me to add a shell command to a list of jobs to have run on the system when I'm not logged in?
For example:
I SSH into my system, decide that I want to read an ebook later, ...
3
votes
2answers
268 views
Is there a workaround for a lack of scheduler in qbittorrent?
Unlike many other torrent clients, qbittorrent comes without a scheduling tool. Ideally, one can throttle downloads over a certain time of the day, on given days.
Is there a workaround for this? Is ...
3
votes
2answers
277 views
How can you determine which process scheduler is being used?
I.e. is it the O(1) scheduler, the CFS scheduler, or an older one?
3
votes
1answer
148 views
Unix/Linux process scheduler logs
Where can I actually see what decisions did a process scheduler make over a time period? Are there scheduling specific logs maintained by Unix/Linux systems I could take a look or should I be looking ...
2
votes
1answer
113 views
What makes the Linux scheduler seem unpredictable?
The question refers to the output of a multi-threaded application, where each thread merely prints its ID (user assigned number) on the standard output. Here all threads have equal priority and ...
2
votes
3answers
87 views
scheduling background tasks in succession
I've got three SAS programs to run in the background over a weekend. The three programs output information into files of the same names, so I'll need to remove these output files after the first ...
2
votes
3answers
702 views
Conditional crontab command in bash script
How do I invoke a crontab command so that I can schedule to run a script with a 20 minute delay based on some condition?
Edit: What if I wanted a command that schedules a script to be executed only ...
2
votes
4answers
336 views
Is there any handy command line tool to manage Cron jobs?
Would someone suggest any handy command line (NOT web) tool or script which adds, enables and disables Cron jobs? I am looking, for example, for the following (or similar) behavior:
sh manageCron.sh ...
2
votes
3answers
98 views
How can I schedule a python program to run from another python program?
I'm running a Python program on my Linux server, and depending on some external data it has to run again at xx minutes or hours from now.
So let's say it runs at 6 AM, and then it has to run again at ...
2
votes
3answers
403 views
Bash while loop and reading from pipe
I have a Windows command-line program that I'm running in a Bash script in Ubuntu via wine. The Bash script basically looks like this:
wine myprogram.exe | while read line
do
# Process line
done
...
2
votes
1answer
180 views
Get pid of long running command executed via at
I would like to spawn a persistent netcat server. My command of choice is the following:
echo "bash -c \"while [ 1 ]; do nc -l -p 1111 >> check; done\"" | at now
I am wondering how I can get ...
2
votes
1answer
599 views
What happens the most, context switches or mode switches?
Which happens the most, context switches or mode switches?
I have two answers myself, but I do not know which one is correct:
Context switches happen in user mode, but this does not mean that a ...
2
votes
3answers
727 views
How to schedule something run once using anacron?
Frequently within my scripts I schedule auxiliary tasks for later in the form:
at now + 8 hours <<< "rm -f workfile.$$ >> $worklog 2>&1 "
or
at 11pm + $(date +%M) minutes ...
2
votes
3answers
565 views
How to monitor or kill a process which has been started by cron?
I have some bots, which are run by the System scheduler at given time interval. But sometimes due to some logical error I have to stop these bots manually. How can I find these processes run by the ...
2
votes
0answers
54 views
So the design of client-server separation is not the bottleneck of X Window?
In the answer of this, it mentioned:
People also hear that X uses the "network" and think this is going to
be a performance bottleneck. "Network" here means local UNIX domain
socket, which has ...
1
vote
3answers
232 views
Faster delayed execution than 1 minute?
I am working on a program that can "upgrade itself" by install a new package. In order to accomplish this, I am using the at command to specify that a shell script should be run one minute in the ...
1
vote
1answer
41 views
Are threads which are executing blocking system calls awoken by interrupts?
I've been reading a bit about threads and interrupts. And there is a sections which says that parallel programing using threads is simpler because we don't have to worry about interrupts.
However, ...
1
vote
1answer
292 views
Disk Scheduler in Linux
I am studying about Disk Scheduling in my OS class. Thought about the disk scheduler in Linux. When I run
cat /sys/block/sda/queue/scheduler
noop anticipatory deadline [cfq]
Someone explain about ...
1
vote
1answer
242 views
controlling priority of applications using cgroups
I would like to understand cgroups better and would like to understand the use-cases for applying cgroups.
Are cgroups a good way for prioritizing different applications (i.e, giving higher priority ...
1
vote
1answer
346 views
Scheduled task on reboot
How can I schedule a task to run on next reboot?
I understand that we have tools like cron and at to help with scheduling. But they seem to allow scheduling at a specific time and not on specific ...
1
vote
1answer
57 views
Do kernel counters for jiffies in state exist in Linux?
I am looking to get time/jiffie stats on the state of a daemon process. The states I'm referring to are mentioned in the Linux Kernel Proc Filesystem document. Running, Sleeping, uninterruptible ...
1
vote
2answers
26 views
What does “INFO: task XXX blocked for more than 120 seconds” exactly mean on Linux?
I had this message in my kernel log. I would like to know what it means technically: under what conditions does the kernel display this message about a task?
For the record, my blocked task was ...
1
vote
0answers
16 views
Get process's timeslice in user mode [migrated]
How can I get the value of process's timeslice in user mode? I designed a new scheduling policy, and I want to check if processes with the same policy (my policy) have the same timeslice to run. It is ...
1
vote
1answer
33 views
How to trace process scheduling of certain process?
For a project at my university I am researching ways to trace, log and manipulate the process scheduling of certain processes. I would like to launch an number of applications, everyone in a single ...
1
vote
0answers
56 views
at daemon creates empty tasks
I have problem with atd daemon. If at is called by non-root, it creates task, but it is empty (content of /var/spool/atd). I do not remember what I have done before it broke that way. What else ...
