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Questions tagged [real-time]

The tag has no usage guidance.

0
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0answers
19 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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0answers
36 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
votes
1answer
84 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)
0
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0answers
25 views

How to prevent realtime applications from being interrupted

I have a realtime application whose performance is being affected by the rest of the system. How can I stop that? My application looks like this: #include <sys/timerfd.h> int main() { ...
1
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0answers
17 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
119 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
votes
1answer
37 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
votes
1answer
65 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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0answers
22 views

Multiple Stopwatches with assigned names

I have many tasks on same time and I switch between them a lot. All I want is a Linux (Mint) App with multiple stopwatches to can switch between them, so I can know at the end how long took every task....
0
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1answer
20 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
54 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
168 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
votes
2answers
262 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 ...
0
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0answers
80 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 ...
0
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2answers
3k 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
votes
1answer
263 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 ...
1
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0answers
238 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 ...
0
votes
1answer
217 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 (...
0
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0answers
174 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 ...
1
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0answers
48 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 ...
1
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2answers
2k 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
votes
1answer
172 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
votes
1answer
110 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
66 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
votes
1answer
692 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
votes
1answer
141 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
votes
0answers
57 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
votes
1answer
687 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
votes
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 ...
1
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0answers
169 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 ...
1
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0answers
53 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
votes
1answer
85 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
vote
1answer
439 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
87 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
65 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 /...
1
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0answers
213 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
votes
1answer
752 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
votes
1answer
768 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
votes
1answer
2k 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 . ...
0
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0answers
91 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
votes
1answer
348 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
votes
2answers
492 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 '(...
11
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4answers
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?
1
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0answers
84 views

Realtime Scheduling and hanging processes

This may be a "you are dumb" question, but at this point I'm hoping for just a new avenue to look down. We run some software on various systems at realtime priority (SCHED_FIFO, Priority: 99) To hit ...
1
vote
2answers
528 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 ...
3
votes
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 ...
1
vote
2answers
103 views

Generate raw Ethernet frames with memory preloaded payloads at < 1 ms intervals

I am looking to generate raw Ethernet frames with payload that is preloaded into memory. The Ethernet frames (10-60 full frames) should be generated at 1 ms intervals with no exception. What would ...
2
votes
2answers
879 views

What makes it possible for a `pulseaudio' process to get the nice level of -11?

I noticed that a pulseaudio process on my Gentoo Linux machine has the nice level of -11. But I don't know how it has gained such a high priority regardless of being owned by a normal user. I know a ...
6
votes
1answer
4k views

How to sort ps output to find processes realtime priority and identify processess currently occupied running queue

How to properly identify real-time processes currently occupied CPU queue and count them using ps? I know there is a bunch of fileds like prio,rtprio,pri,nice but do not know correct to use. It seems ...