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Questions tagged [real-time]

The tag has no usage guidance.

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15 views

How to track a file for processes that use this file

I have a script, that listens for file /lib/modules/4.10.0-19-generic/kernel/drivers/media/usb/uvc/uvcvideo.ko and if the file is been accessed then runs the lsof command: #!/bin/sh inotifywait -mrq -...
1
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0answers
59 views

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 *...
1
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1answer
34 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 ...
-1
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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 ...
1
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1answer
55 views

Detect if USB disk is mounted in C application in Linux

I would like to check if USB disk is mounted in a C application. I know that in a script I can accomplish this via mount | grep /mnt (the mount point where udev mounts the USB drive) but I need to do ...
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0answers
24 views

Filter output / print one record per event or time period

I've got a custom HID device which prints out exact coordinates of touched points at real time. It is very sensitive & currently printing out the coordinate that's being touched on multiple ...
0
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1answer
75 views

compile and use a realtime kernel on CentOS 7

I would like to compile and use a realtime kernel on CentOS 7. I found a guide on the web: http://jensd.be/589/linux/complile-and-use-a-realtime-kernel-on-centos-7-or-rhel-7 When I try to use it I ...
-1
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1answer
130 views

Running make -j$(nproc) or make modules -j$(nproc)

I am following this. To run make -j$(nproc) make modules -j$(nproc) I know that make is running jobs Are the jobs supposed to run for hours? (I got impatient and interrupted.) make -j$(nproc)
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0answers
18 views

Activation /Config of Preempt RT [duplicate]

I installed the Preempt RT patch, how can I know if it was installed correctly, and if it was activated? If it was right, what configuration shall be done, and how to do it?
2
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1answer
140 views

Among these two in my ps output, which real-time process will be preempted over the other by linux?

I have got some idea from: https://stackoverflow.com/questions/8887531/which-real-time-priority-is-the-highest-priority-in-linux about how the real time priority values assigned to different ...
-1
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1answer
40 views

Since which version does linux support system clock with nano precision?

We are using centos7 and with the date command we came to know that system clock support nano precision. date +"%s %9N" 1537941601 130559008 So, we were to know that from which version did linux ...
0
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1answer
114 views

Knowing when a write() on a serial port has finished transmitting data

I need to synchronize an IO pin value with a write to a serial port from user space (because I wasn't yet able to do it from kernel space - see my other question). My code (leaving out error checking) ...
0
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1answer
23 views

How to real-time display a number from a running log file or terminal [closed]

I have a CNC and the software runs from a terminal. I would like to catch the current Z axis depth in real-time to display it. The information I need is shown in the terminal as well as in the log ...
1
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0answers
62 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
7 views

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
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1answer
225 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 ...
2
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2answers
357 views

Port Forwarding without delay and high fps in a real time live stream using socat

I am using the command socat to port forward a connection from a real-time live stream. TCP4-LISTEN:8080 TCP4:123.456.789.12:80 The problem is it has added delay and low fps while the live stream ...
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0answers
112 views

Switching off real-time group scheduling in the kernel

Is there a way to switch off the real-time group scheduling in the kernel on Centos 7? I have a real-time service that is managed by systemd. But the cpu.rt_runtime_us value is set to 0 by default. I ...
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2answers
4k views

Current time/date as a variable in BASH and stopping a program with a script

I am trying to create a raspberry pi spy cam bug. I am trying to make it so the new file created for the various processes come up with NOW=`date '+%F_%H:%M:%S'`; which works fine. but it requires ...
0
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1answer
295 views

Enable CONFIG_PREEMPT_RT_FULL after the kernel compilation

I have Linux with a kernel that was compiled with the real-time patch, but the config option CONFIG_PREEMPT_RT_FULL was not enabled (it says in /proc/config that it is not set). Do you now if there ...
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0answers
268 views

Check if Linux Kernel is real time or not from Kernel module

We have a kernel module which is used on both real time (RT) and non-real time Linux kernel. Module uses the function get_user_pages_remote. However, there is a version check since the module needs to ...
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1answer
244 views

Applying RT PREEMPT kernel patch fails

I am trying to apply the RT PREEMPT patch for the Linux kernel. As mentioned in guides like this and this, you are supposed to do it like this: zcat patch-4.14.15-rt13.patch.gz | patch -p1 (...
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0answers
201 views

Configure raspberry pi kernel from script instead of menuconfig

I would like to build the official kernel for the Raspberry Pi. But I want to change one feature during the process. I'm basically following this tutorial: http://www.frank-durr.de/?p=203 And at ...
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0answers
57 views

What are the performance implications of isolating a core vs PREEMPT_RT?

I try to figure out what the differences between several real time systems are. So far I've tried to use the PREEMPT_RT patch and to isolate a core and reserve it for the RT application. So far I've ...
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2answers
3k views

How to find scheduling policy and active processes' priority?

I want to make a shell script that finds all active processes and to print to the user the scheduling policy.I want the result to be like this. pid 3042's current scheduling policy: SCHED_OTHER pid ...
0
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1answer
201 views

Interpretation of PTP4L and PHC2SYS syslog records

I'm using the ptp4l and phc4sys services to syncronize the clocks of my Centos 7.4 servers to a central PTP source. The services regularly write syslog records like the one below. I haven't found any ...
0
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1answer
123 views

Where to find extended information about menuconfig kernel configuration options?

Where to find extended information about menuconfig options? I am especially interested in those related with improving latency/jitter of a RT_PREEMT kernel (apart of the obvious ...
1
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0answers
75 views

rtcwake being set one day ahead of intended time

I am trying to use this command to wake up my computer 5 seconds from now: sudo rtcwake -m no -s 5 The problem I am having is that the time to wake my computer is set 5 seconds ahead of current time ...
2
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1answer
790 views

Docker with real-time / low-latency audio? (for virtual amps like Guitarix…)

I've been trying to get a foss virtual guitar amp to run on my Fedora machine for a while now, Guitarix (which runs on JACK) to be more precise. But I just can't figure it out. People say that it is ...
2
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1answer
156 views

lxc and sched_setscheduler

I am trying to run an application inside a Centos container and needs to run in real time. I googled around and the suggestion was to add lxc.cap.keep = sys_nice. After I did it, lxc-start complains ...
2
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0answers
61 views

Time between process runs is occasionally too long, how can I set a maximum time? [closed]

I am using a raspberry pi to grab data through a SPI port. Attached to the SPI port is a PIC, programmed so that it samples on an A/D at 12.8kHz, and stores the samples in a 256 long buffer. (to cope ...
3
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1answer
784 views

Clock instability in Debian 9 (stretch)

I have a machine running Debian 8 (jessie) downgraded to kernel 3.2-rt. This is running an application which is set to realtime priority (SCHED_RR), wakes up every 1ms to do some processing, and ...
2
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1answer
2k views

How to run real-time application in Linux?

Trying to get working LinuxCNC on my Debian Jessie, I did: Installed the kernel 4.9 RT through Jessie backport using apt-get/aptitude. Restarted my computer and checked uname -a contain PREEMPT RT ...
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0answers
173 views

Raspberry Pi RT Preempt Linux Kernel Build Error

I am trying to Build and install a Raspberry Pi RT Preempt Linux Kernel. These are the steps that I had followed: I installed the pre-compiled kernel kernel-4.4.9-rt17.tgz I downloaded Raspberry Pi ...
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0answers
56 views

Is realtime kernel error corrected for system clock? [closed]

I realized that it is RT-Kernel. The system clock I use usually has an error (although it is corrected using rtc, but there is a system clock error anyway). I realized that it was RT-Kernel and I ...
0
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1answer
87 views

systemd: start openvpn.service after time has synced

I use systemd-timesyncd to sync the time on my system. It doesn't have a battery to save the RTC. When I connect it to the internet it takes about 30 seconds to sync the time. I would like to reduce ...
1
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1answer
497 views

Can SCHED_FIFO be preempted by SCHED_DEADLINE?

As stated in the man pages: A SCHED_FIFO thread runs until either it is blocked by an I/O request, it is preempted by a higher priority thread, or it calls sched_yield(2). From the same source: ...
3
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1answer
91 views

Is possible to focus single core on very realtime calculations while using others as regular cores?

I am finishing part of project I started while ago and I need decent kernel for it. There is code that is critical to be ran all the time, as latency bigger than 1us may have impact on quality of ...
0
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1answer
66 views

Make Linux responding even when there is an I/O Error

WHen there are harddisk's I/O error, my computer becomes unresponsive (mouse cannot be moved, screen freezes for a moment, keypress does nothing), for example when executing: sudo fsck.ext4 -fckyvt /...
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0answers
221 views

VM and host time drift during suspend

I am running Ubuntu 16.04 on my laptop, with Ubuntu 14.04 in a Vagrant VM in VirtualBox. My laptop is running SystemD and network time is enabled: naftuli@reprisal:~$ sudo timedatectl status ...
4
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1answer
849 views

realtime pthread created from non-realtime thread with init.d

I have a piece of C++ code that runs just fine when I run it from a Linux terminal, but which throws an EPERM error when run from a SystemV (init.d) script on bootup. The error comes from a ...
4
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1answer
815 views

Record time of every process or thread context switch

I'm trying to get the nearest to real-time processing I can with a Raspbian distribution on a Raspberry Pi for manipulating its GPIO pins. I want to get a "feel" for the kind of performance I can ...
3
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1answer
3k views

“tail -f” using “tcpdump -r”

To display content of pcap file , we use : tcpdump -r /Path/to/syscontection.pcap; However, this command line does not follow the pcap file on realtime , like tail -f which follows a plain text . ...
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0answers
95 views

How to install real time patch on Embedded Linux version 3.16.0

I have a microprocessor that runs the embedded linux version 3.16.0-rc3 (armsdk@debian, gcc version 4.7.2 (GCC)). I wanted to install a real time patch, but I did not find the one for my linux version....
2
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1answer
366 views

Applying RT_PREEMPT

I'm trying to install a kernel with the RT_PREEMPT patch on a Lubuntu 16.04 distro and running into some issues I'm not sure how to deal with. I've downloaded the sources for kernel v4.4.12 (linux-4.4....
3
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2answers
558 views

how does the gnu coreutils `date` work? [closed]

I did not see any similar questions on this site. The manpage, while helpful in describing how to use date, did not have much background info. Even the info page (as prescribed in the manpage: info '(...
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5answers
4k views

Real time cmd tool to show HDD space remaining

Is there a command line tool which shows in real time how much space remains on my external hard drive?
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0answers
87 views

Realtime Scheduling and hanging processes

We run some software on various systems at realtime priority (SCHED_FIFO, Priority: 99) To hit certain frame requirements in the software our engineers work on. one of our side projects doesn't "...
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2answers
589 views

Tracking/Monitoring Short-Lived CPU-Intensive Process on one CPU

So I've been working with this issue for some time now, and I'm having trouble finding the tools to troubleshoot this problem, which I have to imagine exist. So here's the basics of my problem: We ...
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0answers
23 views

Limit access/transmit rights on NIC to a single user application

I currently have a RT patched linux machine and I need to have full and undelayed access to my Wired interface card. I am running a realtime non-preemtable user application which sends a couple of ...