Questions tagged [scheduling]
A technique for scheduling tasks to be run at a specific time or on a specific event.
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How to set the SCHED_RR time slice or time quantum per process / thread?
The time slice (also called time quantum) for threads with SCHED_RR policy can, according to the sched_rr_get_interval man page be obtained using
int sched_rr_get_interval(pid_t pid, struct timespec *...
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1answer
29 views
Realtime, SCHED_FIFO, CPU_SET()
I'm trying to assign two real time processes to two cpus(one each). I'm using SCHED_FIFO scheduling policy.
I'm doing the following things:
adding "quiet splash isolcpus = 6,7" at ...
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0answers
15 views
Real time, cpusets, sched_setaffinity [migrated]
I'm trying allocate a specific core to a realtime thread(sched_fifio or sched_deadline). while attempting that I've tried the following in the code.
used CPU_ZERO() to clear all the cpus allocated to ...
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2answers
35 views
Slurm like alternative for localhost
I have resources (e.g. GPU) I can only use once at a time. When performing experiments I always need to know on time of a batch files creation, what experiments I want to execute in the future. But I ...
0
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0answers
38 views
rcu_sched self-detected stall on CPU + watchdog: BUG: soft lockup - CPU#3 stuck for 22s
Being unable to ssh into a machine I connected it to a monitor and found the following:
The machine is running Ubuntu Server 18.04 LTS and is a first generation 8 core Ryzen 1700. I've restarted the ...
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0answers
34 views
Priority scheduling with same priority and arrival time [migrated]
In priority scheduling, scheduling is based on priority of process, then arrival time. What if both process have same priority and different bust times
For example:
Case 1
in order of (Process. AT. ...
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0answers
20 views
Determine average and maximum execution time of a task by using ftrace/perf
I've gathered some traces containing scheduling events ('sched:*') by using ftrace and perf record. By analyzing the results many of my questions could already be answered.
However, I was wondering ...
2
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1answer
29 views
How can I visualize the scheduling domains on Linux?
It seems current versions of Linux use scheduling domains to distribute processes between CPUs, hyperthreads, NUMA nodes, etc.
Say I wanted to visualize the domains that exist on a system, and some ...
2
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0answers
58 views
ext4 jbd2 and I/O priority
I want to delete a huge directory with over 6 million files across over 4000 directories, totaling about 26GB of data. As I knew this was going to take a while I used ionice to set the I/O priority ...
0
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0answers
14 views
Range of values of virtual runtime in CFS scheduler
I am trying to understand the working of the Linux CFS scheduler using kernel version 4.19.2.
As mentioned in the documentation, it does not use timeslices in the traditional way but uses the concept ...
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3answers
343 views
What's the advantage of mere Ansible on mere shell-scripting if one doesn't use communally-maintained Ansible-Galaxy roles? [closed]
I establish a LAMP with a few extras on a remote Debian machine with a similar shell (Bash) script:
#/bin/bash
apt update -y
apt upgrade ufw sshguard unattended-upgrades wget curl git zip unzip tree ...
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1answer
35 views
change a value in a file
I have a configuration file that some of its lines is like below:
# Mandatory: no
# Range: 0-5
# Default:
DebugLevel=3
I want to change the 3 at DebugLevel to 5 at 2 AM then after for example 2 ...
0
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0answers
15 views
ionice vs nice for mysqlimport
I am trying to import a huge .sql file into a mysql server.
What (if any) is a best option to speed up the process (all other parameters being equal)
reducing the process niceness to -20?
setting ...
0
votes
1answer
29 views
Is it possible have a deterministic run of linux process inside docker?
Imagine that I have a linux program that does some network IO. Execution of the program is not deterministic: it gonna produce different results depending on how it's threads are scheduled, what ...
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1answer
71 views
What's the process scheduler in Linux?
I read wikipedia about process scheduler:
The process scheduler is a part of the operating system that decides which process runs at a certain point in time.
I don't really understand what that ...
1
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1answer
69 views
Restrict time of day for anacron jobs in Linux Mint
I'd like to restrict the time of day the jobs set in anacrontab are allowed to run.
I can find in man pages online info about START_HOURS_RANGE which is supposed to do precisely that. For example ...
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0answers
8 views
Thread scheduling behavior between steps of GDB compared to non-stepped execution
The GDB manual states that when using all-stop mode for debugging a multithreaded application, it is not possible to advance every thread in lock-step by exactly one statement. This makes sense since ...
0
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1answer
124 views
How to schedule to run testng.xml file on terminal on linux environment?
I have scripted a Selenium automation testcase. I have generated the testng.xml file which should be executed on the linux terminal at a particular time of my need. Say I want to schdule to execute ...
0
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2answers
270 views
How to schedule a command to execute in every 2 hours?
I want to run a small monitoring jar file every 2 hours in my ubuntu machine.
java -jar mymonitoringtool.jar
I don't know how to set it up.
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votes
2answers
56 views
Why is there no choice for cooperative scheduling?
Operating System Concepts says
CPU-scheduling decisions may take place under the following four
circum- stances:
When a process switches from the running state to the waiting state (for ...
1
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0answers
254 views
How linux kernel scheduling works on multi core processor? [closed]
I recently started reading Robert Love's book "Linux Kernel Development 3rd edition" and dived into the scheduler part, which left me with lots of questions.
So first off, I understood there are 2 ...
2
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0answers
28 views
Incorrect Top? or manpage?
According to top's manpage:
16. PR -- Priority
The scheduling priority of the task. If you see `rt' in this
field, it means the task is running under real time scheduling priority.
...
1
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1answer
44 views
FCFS disk scheduling [closed]
I want to find head movement through Disk Scheduling first come first serve algorithm
queue = 98, 183, 37, 122, 14, 124, 65, 67
head start at 53
I have confused because this same quotation two book ...
0
votes
1answer
272 views
/proc/PID/sched measure units
Does anyone know what are the measurement units for the metrics in /proc/<PID>/sched file in Linux?
cat /proc/1277/sched
flush-202:32 (1277, #threads: 1)
----------------------------------------...
0
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1answer
37 views
Is it recommended to use param.sched_priority in Linux FIFO during thread creation?
In my embedded device I absorb strange behaviour with the protocol we use, sometimes it takes a while to send the data via serial device using FIFO.
My suspicion is Linux is not real-time OS and why ...
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2answers
252 views
Meaning of parameter “kernel.sched_min_granularity_ns” in RHEL6/RHEL7
While studying the kernel behaviour from RHEL6 to RHEL7, we came across an explanation on RHEL6 kernel parameters:
> kernel.sched_min_granularity_ns
sched_min_granularity_ns is the initial ...
1
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1answer
176 views
How does the kernel scheduler know a timeslice has passed?
In my previous question How does the kernel scheduler know how to pre-empt a process? I was given an answer to how pre-emption occurs.
Now I am wondering, how does the kernel scheduler know that a ...
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2answers
282 views
How does the kernel scheduler know how to pre-empt a process?
As far as I understand, the kernel is not a process, but rather a set of handlers that can be invoked from the runtime of another progress (or by the kernel itself via a timer or something similar?)
...
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0answers
86 views
How to keep Linux kworker threads alive?
I'm experiencing some data loss on a USB-to-serial adapter on a Raspberry Pi running at a (relatively) high data rate. I believe most of the work is carried out by kernel threads:
2569 root 20 ...
1
vote
2answers
345 views
Giving users scheduling privileges
I have some code which uses sched_setscheduler from sched.h
sched_param sched;
sched.sched_priority = 70;
sched_setscheduler(getpid(), SCHED_FIFO, &sched);
However, this function will fail ...
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0answers
58 views
Linux (kernel 3.x and 4.x) Pthread and general process scheduling algorithms
I was wondering if both scheduling (contention) scopes (SYSTEM and PROCESS) are used in the Linux kernel scheduling logic. POSIX supports PROCESS scope pthreads (MXN model) and SYSTEM scope pthreads (...
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0answers
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sched_deadline behaviour
I've studied the sched_deadline and i have some questions:
1) Is a portion of CPU assigned to sched_deadline algorithm at precise time intervals ?
If yes, who decide how much Utilization Factor ...
0
votes
1answer
204 views
CFS and real-time policies
I'm trying to implement a real-time algorithm in Linux.
I've studied the linux Real-Time policies : sched_rr, sched_fifo.
Than i go deeper and i found the Completely Fair Scheduler.
I deduced that ...
0
votes
1answer
111 views
Does Linux 3.10 CFS have “timeslices”?
Does Linux 3.10 CFS have "timeslices"?
I am confused, because sched-design-CFS.txt clearly states:
CFS uses nanosecond granularity accounting and does not rely on any jiffies or
other HZ detail. ...
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vote
3answers
175 views
How to schedule activation/termination of KVM/QEMU virtual mahines?
I run an IPv4 server in a Fedora virtual machine. This server hosts a git service for a group of developers and is open to the internet. As a consequence, it is confronted to hacking attempts (mainly ...
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0answers
20 views
How to check a process is running in which core? [duplicate]
I have a very computationally intensive job(single threaded) running in my system, and htop is showing one of the core is ~100% utilized. Obviously, the job is scheduled to this core. But, I am ...
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0answers
36 views
During what kinds of operations is a process considered for the 'load average'?
In general, I'm trying to understand the numbers displayed by uptime (and numerous oder commands):
$ uptime
13:40:52 up 18 days, 2:10, 8 users, load average: 0.20, 0.30, 0.64
Here, my system's ...
2
votes
1answer
1k views
Kubuntu 18.04, cron task does not load @reboot
I am running Kubuntu 18.04, and have a simple script to reset the plasmashell every time after suspend/lockscreen since there's a known bug that corrupts folder/file names upon returning from suspend.
...
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0answers
33 views
How to find the tree of schedulable entities in Linux?
I am trying to set the nice values of my VMs (KVM + QEMU). I do this by:
ps -u libvirt-qemu # get pid of qemu-system-x86_64 process.
ls /proc/${PID}/task/ # get pid of the CPU 0/KVM thread.
renice -n ...
1
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1answer
180 views
Set usb flash drive as non rotational drive
I'm trying to optimize the IO schedulers and to use a proper scheduler for rotational and for non rotational drives (different).
When I run:
cat /sys/block/sd*/queue/rotational
I get:
1 <-- ...
2
votes
0answers
191 views
Shielding CPU from scheduler - How to move bound kernel threads from cores?
Suppose I have 4 physical cores (indexed 0-3) and I'm dedicating cores 1-3 to a shield for user applications and trying to steer all system threads onto core 0. I'm following the answers here and ...
1
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1answer
58 views
Why will crontab not run my file at a set time, but will run every minute?
So, I have attempted to get crontab to run a node.js file at a set time everyday. I have set it up by doing crontab -e. I have tested that it runs every minute by using the below:
* * * * * //path of ...
0
votes
1answer
1k views
Custom priority value: is a pthread high sched prio positive or negative?
I’m trying to reimplement in a backward-compatible way the RobotC API from C (although some details would better fit or would be easier with C++), and trying to reimplement their multithreading API in ...
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1answer
270 views
How to troubleshoot failing cron job
I have a crontab root file that looks like this:
lab-1:/var/www/cdd# crontab -l
# do daily/weekly/monthly maintenance
# min hour day month weekday command
* * * * *...
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0answers
55 views
Why is my scheduling policy is 0 (SCHED_NORMAL) but priority is 20 as well?
I have a device which is running linux 2.6.36.
There is no file, "sched", in /proc/pid. So I use /proc/pid/stat to see what priority is being used.
The "stat" shows (as below) that my priority is 20 ...
0
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1answer
402 views
What happens when there is a context switch while the process is in Kernel mode?
This is my understanding:
When in user mode and a trap/system call occurs, registers are saved on to the kernel stack, switch is made to kernel mode, and trap is handled and returned to user mode.
...
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0answers
113 views
How to iterate tasks in a cgroup, one cpu at a time, holding runqueue's lock?
I want to achieve 3 goals.
Iterate tasks through a task_group
Aquire rq those tasks attached to.
Group those tasks by rq, then lock the rq before iterating tasks (the reason for this: I want cfs_rq ...
1
vote
1answer
28 views
Does increasing the niceness of processes reduce time spent on scheduling?
Suppose a server has many long-term cpu-bound processes with no realtime requirements for those processes. Would maximising the niceness of each process reduce cpu time spent on scheduling those ...
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1answer
2k views
How to disable blk-mq for NVMe and use CFQ, deadline, noop?
For testing purposes, I would like to use CFQ, deadline, and noop for an NVMe drive. Is this possible?
I am able to use the blk-mq for SATA SSDs by adding "scsi_mod.use_blk_mq=1" to the grub boot (...
3
votes
0answers
51 views
What is the maximum processor frequency that Linux could run on?
Theoretically, if an extremely fast computer could be built (100s of GHz or even terahertz), what is the maximum frequency that could be expressed in the variable used by the scheduler allocate cycles?...
