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Questions tagged [latency]

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Solving the USB drive/mass storage stall issue

Sadly the issue reported and described here: Pernicious USB-stick stall problem. Reverting workaround fix? and Is "writeback throttling" a solution to the "USB-stick stall problem"?...
Artem S. Tashkinov's user avatar
0 votes
0 answers
30 views

iperf3 doesn't find network bandwidth difference but curl does

I have 1 client (A) and 2 servers (B & C). Servers were using different amounts of CPU with load balancing and i wanted to root cause it. I suspected it could be a network speed issue so I ran an ...
Erich Shan's user avatar
1 vote
0 answers
66 views

SSH client with instant input echo

When using the terminal on code-server (VSCode probably does it as well), input is instantly shown on screen (grayed out, until the server actually responds): When I connect to the remote machine ...
LHLaurini's user avatar
  • 233
0 votes
1 answer
224 views

How to measure TCP latency?

OS is Debian on both servers. I found some examples showing how to measure TCP latency with nmap: nmap --packet-trace -p 22 192.168.0.10 But I'm getting some negative results for latency. ie, it will ...
cat pants's user avatar
  • 487
2 votes
2 answers
8k views

How do you install the linux-lowlatency kernel and why does it stops at version 5.15?

I have been reading today about linux-lowlatency and I am more and more confused. First of all, is the install as simple as sudo apt install linux-lowlatency and then reboot? Do I need to select a ...
Mathieu's user avatar
  • 117
-1 votes
1 answer
75 views

http latency wild variance on localhost

Running on MBP M1 with 10 cores. Running 1 thread client (wrk) and 1 thread server (java). A youtube is also running on the system. Load average 2 out of 10. Except GC, which could be the reasons of ...
NicuMarasoiu's user avatar
0 votes
1 answer
781 views

vim very slow over SSH connection

I have a non-stellar SSH connection to some machine; the echo time is... I don't know, 0.2 seconds or so. Anyway, when I start vim, say with no input file, I experience a long delay, of about 3 to 4 ...
einpoklum's user avatar
  • 9,652
2 votes
1 answer
373 views

strange issue, worst network speed and worst ping latency on linux

I cannot explain this, I will start by listing these speed test results this one is the linux host running mxlinux latest version this one is the windows 10 running inside vmware on the same computer ...
Fredou's user avatar
  • 131
0 votes
0 answers
252 views

strace with errors on openat syscall with Lustre FS, RHEL 8, overall intermittent latency

Does anyone see what could be causing this intermittent latency? At various times all commands become slow on login, compute and head nodes and only with logins associated with Lustre, i.e., root and ...
RobbieTheK's user avatar
1 vote
0 answers
333 views

How to tune Linux kernel to try to keep free RAM ready?

I have a system with very spikey memory usage and lots of disk activity. As such, I'd like to have files in the cache as much as possible but I'd like to have enough free RAM ready to go to quickly ...
Mikko Rantalainen's user avatar
1 vote
1 answer
798 views

How to change the default BDI `max_ratio` and/or `min_ratio` for all devices?

I'm using a system with multiple storage devices with different write throughput. As explained in question Why were "USB-stick stall" problems reported in 2013? Why wasn't this problem ...
Mikko Rantalainen's user avatar
0 votes
1 answer
550 views

Reduce microsecond jitter (using realtime kernel)

I have a raspberry pi 4B running Gentoo, with the 5.15.44 raspi kernel & realtime patches applied to it. The kernel is configured for CONFIG_PREEMPT_RT (big surprise), as well as ...
xNaXDy's user avatar
  • 1
1 vote
0 answers
236 views

Add extra latency on top of existing tc qdiscs

On a system with an existing multi-stage qdisc setup, we need to introduce extra latency (at least fixed, but fixed with a small variation would be a nice option to have). The canonical way to do this ...
mirabilos's user avatar
  • 1,752
0 votes
0 answers
413 views

Low-Latency method to read Xorg or DRM framebuffer

I am trying to build an application that can measure the latency/processing time of graphics frameworks on Linux. My idea is to implement simple programs that react to an input event (e.g. mouse click)...
Andreas Schmid's user avatar
0 votes
1 answer
741 views

Copying a same file multiple times

I have an audio file, and I am running a script to decode that audio file. Now I want to measure the latency of the system. So, I am running a script with a time command. like $ time ./uber.sh In the ...
adikh's user avatar
  • 125
1 vote
0 answers
546 views

How to increase the latency of the microphone?

I'd like to increase the latency of the audio output. Configuring latency offset on pavucontrol doesn't work. I first typed: pactl load-module module-loopback latency_msec=2000 source=alsa_input.pci-...
Tenzin Dorje's user avatar
1 vote
1 answer
543 views

How do I change the default SYN retransmit exponential backoff in Linux?

By default, if a SYN packet is not responded within one second, linux sends another one under the assumption that the first one was dropped somewhere. Then another after two more seconds, then four, ...
Thomas's user avatar
  • 228
1 vote
1 answer
442 views

What may cause huge latency while ssh

I'm working on a local Windows and three remote CentOS7 Linux servers. The three servers are under the same gateway. The IPs of the three sesrvers are: 170.35.31.104, 170.35.31.105, 170.35.31.106. I ...
Yves's user avatar
  • 3,331
2 votes
1 answer
2k views

Linux Completely Fair Scheduler and sched_latency_ns

I thought I understood CFS but... The scheduled latency is the time that in which every runnable process can expect to get a share of the processor. In the Linux Kernel code it gives: (default: 6ms *...
Mike James's user avatar
1 vote
2 answers
1k views

Test network latency from one machine to another (or to a specified target endpoint) over TCP?

Are there any free command line tools for testing network latency from a machine A to machine B over TCP where machine A is running linux? I need to test for a large number of small e.g. GET requests ...
u123's user avatar
  • 971
5 votes
2 answers
6k views

Low latency vs normal kernel?

I am new to this world, and I want to make and record music with my new Linux installation, as I have found marvellous applications. I have seen some youtubers recomending to install the linux-...
ivanovitx's user avatar
86 votes
4 answers
50k views

Why would anyone choose not to use the lowlatency kernel?

I can't find any good information on the rt and lowlatency Linux kernels. I am wondering why anybody would not want to use a lowlatency kernel. Also, if anyone can tell what the specific differences ...
Startec's user avatar
  • 1,909
5 votes
3 answers
7k views

How to keep a local directory automatically synced with a remote, without latency issues?

I develop a git-tracked codebase that has a lot of files. This code must be run on a remote machine. So every time I make a change locally, I must then sync it to the remote and run the new code on ...
Donentolon's user avatar
2 votes
1 answer
367 views

Is there a way to sort IPs by latency?

Given a list of IPs, how can it be sorted so that the "nearest" or lowest latency is sorted to the top, "farthest" or longest latency, is at the end?
Rich's user avatar
  • 843
0 votes
0 answers
372 views

Difference in script latency output and ping command

I've written a python script that executes 1 ping to 8.8.8.8 and prints the latency output to the console (output "py_script:..."). After each print, the process sleeps for 1 second. I do only 1 ...
imll's user avatar
  • 219
1 vote
0 answers
420 views

How to measure software + hardware latency using tcpdump? ( Hw Timestamp)

I have an low latency application.But it's performance is unstable. So i want to find the bottleneck if it's related to network or related to my server ( software , os etc.) So first i tried tcpdump ...
afceke's user avatar
  • 11
2 votes
0 answers
418 views

Linux: How is the input latency of a Wacom tablet distributed among the various software- and hardware components?

Say I have the following setup: Linux Kernel input-wacom kernel driver xf86-input-wacom X11 driver Wacom tablet How is input latency distributed among these various components? Are there any ...
Árni Dagur's user avatar
1 vote
1 answer
2k views

Simple file copy (or write) causes ten second+ latency on Linux filesystem

I am running Linux on a spinning hard drive. WDC WD5000LPLX-7, "WD Black Mobile", 7200 RPM. I noticed a simple file copy (or write) causes fsync() latencies of over ten seconds. Is there some way ...
sourcejedi's user avatar
  • 51.1k
0 votes
1 answer
3k views

What is the meaning of fragments and fragment_size in PulseAudio ALSA modules?

Following advice on a blog post called Pulseaudio And Latency, I tried loading module-alsa-sink with special fragments and fragment_size parameters to ensure low latency. However, I'm not sure what ...
Metamorphic's user avatar
  • 1,209
1 vote
1 answer
1k views

What are the differences between qperf and ping test latency results?

I am wondering what are the differences between qperf and ping tests latency results. In terms of measuring latency between two servers which tool result could be considered more accurate? ping: ...
Bustam's user avatar
  • 143
2 votes
2 answers
671 views

How to debug program latency?

I'm trying to run amsynth on a rpi. Latest version of raspbian, fresh install. I tested amsynth on my x86 desktop and it works great, no latency. On the rpi however, I get a delay of around 1 sec ...
cat pants's user avatar
  • 487
1 vote
3 answers
3k views

Better performance for music production using Wine or Windows-on-Virtualbox (on Linux host)

There are two applications that I have used and familiar with on Windows 7 and 10, and would like to use also on my new Desktop running Ubuntu (with lowlatency kernel), i.e. Guitar Rig 5, and FL-...
bdutta74's user avatar
  • 171
3 votes
1 answer
805 views

How can I determine if a latency is due to a driver or the scheduler?

Using an oscilloscope and toggling some pins I sometimes see latencies of 1-2 seconds from when an 8-byte UART packet is transmitted to when a blocking read returns. The packets are 1 second part with ...
Kenny's user avatar
  • 165
5 votes
2 answers
5k views

Why would SSH freeze for minutes at a time when other traffic is unaffected?

I've noticed when I SSH into a remote machine over a slow link, SSH seems to "stick" after a relatively large amount of data is transferred. For example, typing text over the link is fine, but ...
Malvineous's user avatar
  • 6,993
2 votes
1 answer
2k views

High network latency after incoming UDP bursts [closed]

This has been crossposted to https://forum.rocketboards.org/t/high-network-latency-after-incoming-udp-bursts/1266 I have an application sending UDP packets over a RAW socket (defining ETH, IP and UDP ...
Stephan Kempkes's user avatar
3 votes
2 answers
5k views

How to find out a CAS latency on my SODIMM DDR3 module?

I have a HP Probook 6470b laptop with HP MBO 179C and Intel mobile HM76 chipset. I would like to find out a CAS latency of my DDR3 memory module without opening the laptop. I was told that the SMBus ...
Hrvoje T's user avatar
  • 1,031
6 votes
1 answer
3k views

Do kernel threads seem to interfere with full tickless mode?

I'm trying to disable local timer interrupts for low latency. I have full tickless mode enabled in the kernel config and I have the boot parameter nohz_full set for the cores in question. However ...
Nathan Doromal's user avatar