Questions tagged [scheduling]
A technique for scheduling tasks to be run at a specific time or on a specific event.
387
questions
0
votes
0
answers
23
views
How to get schedule delay information of each cpu?
I know that the scheduling information of each process can be obtained from procfs, but I don't know how to get the schedule delay information of each cpu. It's better to use procfs or syscall.
1
vote
1
answer
24
views
chrt fails to set policy - Invalid argument
This happens both on Fedora and Garuda. Here are example error messages:
$ sysctl kernel/sched_deadline_period_min_us kernel/sched_rt_period_us kernel/sched_rt_runtime_us
kernel....
0
votes
0
answers
32
views
Linux kernel BUG: scheduling while atomic: swapper/0/0/0x7fff0001
I'm running Arch Linux, kernel 5.17.3 (though this issue has been happening across many versions.) Every couple of days, I get random complete system freezes. The kernel logs vary, but they most ...
-2
votes
1
answer
54
views
Where and how is the scheduler running? Can I "see" it? [duplicate]
The scheduler is not a thread but it's a kernel function, so there's no way to actually "see" what the scheduler is doing (I assume). These particular kernel parts are kind of invisible from ...
-2
votes
1
answer
54
views
Where is the process scheduler running? Can I track it?
Is the process scheduler "visible" at user space? Can I see it with ps? Maybe is it one of the kernel threads? If yes, how is it called? How can I "see" it?
It doesn’t exist as a ...
0
votes
1
answer
17
views
Finding default process scheduler
Where in the Linux code, I can find the default process scheduler at the time of launching a process. For a running process, chrt shows SCHED_OTHER. On the hand, in various websites, I see that the ...
0
votes
1
answer
53
views
No sched_min_granularity_ns in kernel parameters
According to this post, there are three kernel parameters for controlling process scheduler:
kernel.sched_min_granularity_ns
kernel.sched_latency_ns
kernel.sched_wakeup_granularity_ns
However, on my ...
2
votes
1
answer
67
views
System-wide scheduling modification
Is there a way to change the process scheduling policy of the whole system? For example, I want to change the default SCHED_OTHER to SCHED_RR for all processes. The command chrt operates on a process. ...
1
vote
2
answers
53
views
chrt has no effect on changing scheduling policy
I would like to change the scheduling policy of a process via chrt, however, as you can see below, it has no effect on the systemd process. This is an example and I tried other processes, too. It ...
2
votes
1
answer
25
views
Adding more schedulers
I have seen different IO schedulers in tutorials, e.g. cfq, noop, but when I test on my linux, I don't see them.
$ cat /sys/block/sda/queue/scheduler
[mq-deadline] none
$ uname -r
5.13.0-27-generic
$ ...
2
votes
0
answers
35
views
How to stop the kernel from pausing my thread?
I have written a software PWM generator for the raspberry PI 4 (Debian Bullseye, kernel 5.10.92). It is a multi-threaded program and one thread is the PWM generator. It is supposed to run ...
1
vote
3
answers
110
views
What config value should I set to make the HZ value (jiffies) physically correct?
When building linux kernel Image, we set the value HZ. linux kernel has the default HZ value. It is a software clock frequency the kernel operates at and 1/HZ (=jiffies) is the unit of scheduler ...
0
votes
1
answer
43
views
What starts threads in Linux OS?
I am currently investigate a question related to threads in the Linux OS. I know that processes are started by the scheduler in Linux Kernel, but what starts threads inside a process - Linux Kernel ...
0
votes
1
answer
47
views
How does linux decide which core a thread runs on?
I know the linux decides which cores threads run on, therefore, the tasks of each core are guaranteed to be balanced. But where can I see the introductory documentation?
I would like to understand the ...
0
votes
0
answers
8
views
How does Completely Fair Scheduling handle new Processes
I'm currently trying to understand Completely Fair Scheduling (CFS) and stumbled across something I can't understand.
Let's make an example:
I have a process running in the background (for example ...
3
votes
1
answer
26
views
Crontab scheduling for specific option
I need to add a crontab entry which runs every quarter ,on second sunday ,at 02 am.
Which of the below one is correct? the OS is AIX.
00 02 8-14 */3 0 && /myscript.sh
or
00 02 8-14 */3 * [...
1
vote
3
answers
127
views
Running a python script via cron at a random time between 10AM-11PM once every day
I'm on ubuntu and need to run a python script once every day randomly between 10AM-11PM. Right now I've only got it running at a fixed hour, I've seen a few examples but mostly for repetitive tasks ...
0
votes
1
answer
39
views
How does Debian (or OSs in general) handle opening of multiple instances of a program?
How does the OS handle it if I were to open up 10 terminal windows? Does it use multi-threading, or multi-processing? Or is there some other concept that I am yet not aware of? And if I were to run a ...
0
votes
1
answer
193
views
schedule cron job for every hour is not working
I am running a single instance cron job for certain task. My script looks like below:
# every hour interval
0 * * * * php /project/yii daily/order
# every 30 minutes interval
*/30 * * * * php /...
0
votes
0
answers
53
views
Scheduling difference manual execution vs Slurm srun/sbatch
tl;dr A CPU intensive workload ignores the nice values of other processes only when started via Slurm sbatch/srun (not when manually started).
I am running a systemd service which periodically gathers ...
1
vote
2
answers
128
views
Spike in number of page faults with make -j`nproc`
I am running a benchmark to figure out the number of jobs I should allow GNU Make to use in order to have optimal compile time. To do so, I am compiling Glibc with make -j<N> with N an integer ...
1
vote
1
answer
32
views
Linux CFS scheduler: how are tasks stopped?
As far as I understand by reading some SO questions and the kernel docs, in Linux, a task (thread, process, or even a group of tasks) is allowed to execute without interruption during a minimum amount ...
0
votes
3
answers
73
views
What is the easiest way to run a program from time X to time Y?
There is a certain potentially failing process that I want to run until it succeeds, during the night time, say, from 23:00 to 7:00, but not later.
A possible solution would be to:
Add a cron job for ...
0
votes
0
answers
26
views
What is the most efficient way to run a task every X hours of runtime, accumulated over all power-ons?
Let us assume that I have a machine which wakes up at 7:00, does some work, usually for 15 minutes, but sometimes for days (e.g., experiment supervision), and after the works is done, it powers ...
2
votes
0
answers
18
views
How do I flag a process to avoid hyperthreading (SMT)?
Suppose I have an 18 core CPU with SMT enabled, and there are 18 long runnning processes, all using ~100% of a thread. If I start a 19th process, the kernel will schedule it to run on one of the cores,...
0
votes
0
answers
7
views
Is it possible to migrate a task running on non-isolated core to an isolated core?
I am trying to run Real-Time tasks on a separate core. For that, I isolated one core, but the isolated core got out of the scheduler. And Most probably, the tasks will arrive on a non-isolated core.
...
1
vote
1
answer
214
views
Understanding overhead cost of context switching
I've always read/heard that context switching is expensive. I recently started reading Robert Love's "Linux Kernel Development" and have made it through the Processes and Process Scheduling ...
0
votes
1
answer
41
views
Display Sleep / Wake on Schedule
Is there some sort of display keep-awake command that could be scheduled?
I have a machine I'd like to run a dashboard display during certain hours without having to interact with it every day to wake ...
1
vote
1
answer
1k
views
systemctl cannot access service file, Permission denied
On Fedora 35, I create my own service to schedule a backup. I have the script in /usr/local/bin/ and service files plus timer in /lib/systemd/system/
ls -an /usr/local/bin/ prints
-rwxr--r--. 1 0 0 ...
3
votes
0
answers
164
views
SCHED_BATCH description confusing - what does it actually do?
There are several scheduling options in Linux, which can be set to a process with the help of a chrt command line. And I can't seem to grasp one of them... Which is SCHED_BATCH. In fact, it's ...
0
votes
1
answer
309
views
How to run a cron job Sun-Fri at 1 PM and 11 AM on Sat?
am trying to set up a cron job schedule which is supposed to run from Sun-Fri at 1 PM but on Sat I want it to run at 11 AM. I am trying this URL to create a cron schedule but doesn't seem to figure ...
1
vote
1
answer
197
views
Linux equivalent of Thread Director?
The 12th Generation Intel chips are rumoured to have "Efficient" and "Performance" cores. Apparently Microsoft's Thread Director, in Windows 11, takes advantage of them.
What will ...
0
votes
1
answer
127
views
How does the page table of a process knows which page was swapped?
I'm refering to those links:
Page table content when the physical page we are looking for is in swap area
how does linux update page table after context switch
How does the kernel address swapped ...
0
votes
0
answers
34
views
How can Linux fair scheduler allow two web servers to listen for requests on one cpu?
If two web servers are on one CPU, with IFS, each allocated 500 millicores (for example, in Kubernetes), how can the kernel be listening on two ports at any given time?
For example, if two requests ...
1
vote
1
answer
40
views
Tools for batching N commands over L scripts (for N≫L)?
Let's say that I have access to a high-performance Linux cluster equipped with a scheduler (e.g. LSF, Slurm, etc.) that will allow me to have up to M jobs either running or pending at any one time, of ...
3
votes
0
answers
118
views
systemd niceness and scheduling configurations not effective in processes performance
My team inherited the care and maintenance of code for a service that runs three python scripts and creates processes which play a part in sending data from our product to another product. One process ...
0
votes
0
answers
55
views
Do higher priority SCHED_RR real-time tasks completely starve all lower priority tasks if there are enough of them?
I'm reading through the man page for scheduling and the description for the round-robin real-time scheduling policy seems ambiguous to me:
SCHED_RR: Round-robin scheduling
SCHED_RR is a ...
0
votes
0
answers
55
views
smp: csd: Re-sending CSD lock (#2) IPI from CPU#89 to CPU#32
Seeing this log,
smp: csd: Re-sending CSD lock (#2) IPI from CPU#89 to CPU#32
What is the reason causing this log?
any idea to improve it?
0
votes
0
answers
218
views
Cron Script to execute every 14 days starting from a specific date,timezone
All, I am looking for a CRON expression which should run every 14 days(2 weeks) on Thursday. As an e.g. if I execute the JOB on June 24th Thursday , next execution should be on July 8th THU, next is ...
0
votes
0
answers
220
views
How to disable rcu_sched detected stalls warnings
When doing some stress, I will get:
INFO: rcu_sched detected stalls on CPUs/tasks:
According to:
https://www.kernel.org/doc/Documentation/RCU/stallwarn.txt
Stall-warning messages may be enabled and ...
2
votes
1
answer
116
views
How to check if/how often my process is preempted by the kernel?
For the purpose of profiling a program I would like to run it uninterrupted on one CPU.
To do this I use a combination of taskset and chrt:
# taskset -c 1 chrt -f 99 ./my_program
Now my question is ...
0
votes
1
answer
183
views
Crontab not running when mac asleep despite scheduled wakeup
I have a crontab that works as expected when my mac is awake but seems not to run when the mac is asleep even though I've scheduled the it to wake up a few minutes before it's supposed to run. In the ...
0
votes
0
answers
23
views
anacron is given priority over cron
An extract from the book Linux-In-Action
As you can see from the crontab file, anacron is given priority over cron.
the crontab file he is referring is - /etc/crontab
Consider the below scenario
My ...
1
vote
1
answer
1k
views
How to schedule a cron for 1st 2nd and 3rd week and on specific day of week?
I am trying to schedule a cron, where if a month has 5 weeks and 5 wednesdays, script A.sh should run on 1st week wednesday 2nd week Wednesday, 3rd week wednesday and 4th week wednesday, where as on ...
2
votes
1
answer
78
views
Am I making invalid assumptions with regard to my kernel module's shared memory?
I have written a "device driver" (see source code here: https://bitbucket.org/wothke/websid/src/master/raspi/websid_module/ ) that runs fine for most of the time (see https://www.youtube.com/...
1
vote
0
answers
63
views
Is it possible to make a program that goes into continuous Uninterruptible Sleep and is non-killable?
According to my knowledge processes in Uninterruptible Sleep cannot be killed. So I thought - Is it possible to make a program that goes into that state and stays in it without going through other ...
1
vote
0
answers
30
views
Does the Linux Genreic Block Layer prefer Read requests over Write Requests?
Does the Generic Block Layer in the Linux kernel, prioritize read requests over write requests ?
That is without taking the I/O scheduler into account.
0
votes
1
answer
121
views
How to tune the linux Scheduler for parallel computation?
I have a linux machine dedicated to running some parallel computation, and I'm trying to understand how to choose / tune the scheduler, and perhaps other parameters, to extract the most performance (...
1
vote
1
answer
33
views
Full feature Linux scheduler
The scheduler cron processes outputs of programs only sending them via mails or writing them in files. So these outputs can't be assigned for example to a PHP variable (see this StackOverflow question)...
0
votes
1
answer
99
views
systemd timer on boot but not too often
Would it be possible to create a timer that will run a service on a boot, but not more often than once a week?
In my case it would be beneficial to run a TRIM (fstrim) for SSD disk on a boot, but once ...