A technique for scheduling tasks to be run at a specific time or on a specific event.

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3
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1answer
1k views

chrt(): “failed to set pid XXX's policy” on one machine, but not others

I have several Linux machines, all of them running the same kernel (Ubuntu 12.04, 3.5.0-45-generic). On one of them, I am unable to use chrt at all. If I attempt to use it on a new process, I get the ...
0
votes
1answer
30 views

Are the crontabs of users linked?

Our Linux server has a community user that has a crontab for itself. The admins don't want me to schedule my scripts on their crontab because they don't want to take responsibility for my programming. ...
1
vote
1answer
100 views

Execution behaviour of cron

I want to schedule a cron so as to avoid running at midnight. I was thinking a period of 7 minutes. Now, I figured out with 7 minutes of interval, the last cron schedule for a particular day would be ...
6
votes
2answers
167 views

Why are there so few “running” processes?

On all of BSD/Linux/MacOS and Solaris, I made an observation - no matter how busy the system is, top always reports very few (usually 1-2) running processes. According to my limited understanding, a ...
1
vote
1answer
69 views

I/O brings a machine to its knees [closed]

Why, on every Linux I've used, when a program is really I/O bound, it bogs the machine down? It just happened when I (accidentally) tried to make gcc compile a (valid!) 50Mb C file. GCC was so I/O ...
2
votes
2answers
85 views

How can I automate a task on a certain event?

Playonlinux and WINE are great. Finally I can have my favourite games and the joys of Linux without having dual-boot or filling my disk with Windows crap! But some are quite old, and only run on lower ...
3
votes
3answers
215 views

stopping atd job at specified time

I'm trying to schedule download at nights. I have created a atd job which starts download script at 2 AM. Now I want to stop the same job at 7 AM if it is still running. What I'm doing now is just ...
0
votes
1answer
121 views

Replace my recurring task scheduler with some existing product

I have a couple tasks that I like to run periodically: Push all git repositories (5 times a day) Do a virus scan on files (every 90 days) Download backup from server (one a day) For all those ...
8
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1answer
1k views

How is nice working?

sched_setscheduler says : All scheduling is preemptive: if a process with a higher static priority becomes ready to run, the currently running process will be preempted and ...
2
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0answers
355 views

how to stop kernel threads preempting real time user space processes?

I created some processes in user space and tried to visualize its working in kernelshark with the trace recorded using trace-cmd. But kernel processes like the ones shown below are preempting my ...
3
votes
1answer
776 views

Using sched_rt_period_us for setting maximum time between task calls of order of 10ms

I realize sched_rt_period_us and sched_rt_runtime_us are meant to prevent freezing the system in case of runaway RT task. I wonder though, if it's possible to use a small value of sched_rt_period_us ...
2
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2answers
2k views

How to install and use at job scheduling?

I am not clear on the following: Is the process for at available to all linux installations? Or do would I need to do something to "install" it?
2
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2answers
2k views

Can system calls be interrupted?

Please comment on the following sentence: On the standard Linux kernel without the rt patch, interrupts can't interrupt ongoing system calls. The reason why our machine doesn't stop working ...
3
votes
1answer
743 views

Are time interrupts always followed by a scheduler call?

When a timer interrupt occurred the ISR is called to service the interrupt. Is it okay to assume that every timer interrupt ends with a call to the scheduler on which process should continue running ...
1
vote
1answer
305 views

Run command after nice command has finished

I have 3 nice commands that are dumping some databases, and compress assets for a backup. After that, the files should be copied to another server. I'm using this command: nice mysqldump -u user1 ...
0
votes
1answer
42 views

Is there such a scheduler and is it feasible?

I read about a scheduling algorithm called EDD which always works on the next deadline and that is feasible. Would it also be feasible to within each time windows or slice, work on all processor or ...
4
votes
1answer
1k views

How is cron scheduling actually implemented and makes sure scripts run on time?

I want to ask about cron jobs. OK, we place the scripts in the crontab and the cron daemon executes them. Now if I understand this, each minute, cron checks the crontab of each user and executes the ...
4
votes
3answers
15k views

What does “INFO: task XXX blocked for more than 120 seconds” exactly mean on Linux?

I had this message in my kernel log : INFO: task XXX blocked for more than 120 seconds. I would like to know what it means technically: under what conditions does the kernel display this message about ...
2
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0answers
178 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
1answer
299 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
1answer
383 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
927 views

Run a command at a certain time in cygwin

I am writing a bash (.sh) script for cygwin. I want to run a certain command at specific time. I tried the following: echo "test" | at 19:00 but I get the following error: The AT command has been ...
2
votes
1answer
408 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, ...
2
votes
3answers
1k 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 ...
3
votes
1answer
319 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 ...
-4
votes
2answers
97 views

Which Linux distro/mode offers lowest interference when running your own applications?

I'm interested in a Linux distro to build C projects and test their behavior in a very predictable and controlled environment. I'm especially concerned about letting the scheduler deal as much as ...
2
votes
3answers
645 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 ...
6
votes
3answers
4k 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 ...
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0answers
102 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 ...
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0answers
137 views

Client-server app for sending and monitoring asynchronous jobs

I am looking for a desktop app/IDE in which you can: Maintain a list of UNIX/Linux connections Be able to write a script locally in a local editor, not SCP files to the host or writing them on the ...
0
votes
1answer
419 views

How to make a scheduled task based on a file creation time?

The supercomputer I run my Analysis uses SGE to do the job management and requires each job duration not longer than 24 hours. And this feature is causing me quite a headache. Sadly, I was asked to ...
2
votes
1answer
1k 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 ...
4
votes
2answers
2k 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 ...
6
votes
1answer
571 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? ...
3
votes
3answers
2k 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 ...
3
votes
3answers
3k 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 ...
4
votes
4answers
934 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 ...
7
votes
2answers
1k 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 ...
3
votes
1answer
384 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 ...
9
votes
1answer
916 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 ...
14
votes
2answers
764 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 ...
24
votes
1answer
3k 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 ...
9
votes
1answer
4k 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
2answers
3k views

How can you determine which process scheduler is being used? [duplicate]

I.e. is it the O(1) scheduler, the CFS scheduler, or an older one?
3
votes
2answers
485 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
3answers
2k 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 ...
11
votes
2answers
372 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 ...
7
votes
1answer
244 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 ...
2
votes
4answers
788 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
1answer
383 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 ...