Questions tagged [performance]

The speed at which a program runs

189 questions with no upvoted or accepted answers
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133 views

Why does my fresh Debian have a high latency?

The time between clicking and seeing a response is very high. Typing looks very funny, and makes me feel queasy. I think there's about 50-20ms "extra". I would expect a top notch linux distro to have ...
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95 views

What tools can show me the CPU usage that doesn't appear in top/sar?

I have a virtual machine that's using ip_tables to set up some connection forwarding. According to top, sar and /proc/stat, I'm > 99% idle. However, perf says I'm only about 72% idle, with the rest ...
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715 views

Local disc copy at 10MB/s! What could be the problem?

I am running a Debian 6.0.6 (before you ask). I have a regular desktop computer, nothing fancy... but when I copy a file using nautilus I am getting 10MB/s copy speed and the system is completely ...
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582 views

Why if I don't disable nm-applet and xfce4-volumed my startup slows down?

I'm running Xubuntu 12.04, and after I ran the update, my login started slowing down big time. I've dabbled a little bit with the programs in Settings -> Settings Manager -> Session and Startup, and ...
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394 views

Connected external HDD slows down system

I need to connect large external hard disks (with many many files) to a system running Ubuntu. I have no idea how the Linux kernel is treating the inodes for the external drives, but attaching huge ...
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380 views

Perform test of aes-ni and aes module in linux kernel

Since both aes-ni and aes module are available in linux kernel , how can I give it a performance test , to decide which one's faster ?
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636 views

Software raid checksumming slow

On my new 24 disk array I get 900 MB/s of raw read or write using dd to all the disks. When I set the disks up as a 24 disk RAID6 I get 400 MB/s write and 600 MB/s read. It seems to be due to ...
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11 views

PC slows to a halt after I play more than 1 game of Rocket League

Here are my system specs. System: Host: mohammed-pc Kernel: 5.2.1-1-MANJARO x86_64 bits: 64 compiler: gcc v: 9.1.0 Desktop: i3 4.16.1 info: i3bar dm: LightDM 1.30.0 Distro: Manjaro ...
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277 views

How to diagnose slow upload speeds on Ubuntu Server 18.04

I'm currently running Ubuntu Server 18.04 on a home server build to act as a Plex server, among other things. I have it connected via ethernet (with a 5-port switch between it and the router), and get ...
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31 views

Slow wired connection on Linux but normal speed on Windows

I installed Ubuntu, Pop_OS, Manjaro, Neon, and Deepin, to my desktop PC (specs at bottom). My internet speed was very slow, basically unusable. Windows gives a normal 15 Mb down and 10 Mb up, but ...
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1answer
83 views

Improve performance when using “system” call (shell escape) processing large files in awk

I have an awk script that processes very large files that look something like this: K1353 SF3987.7PD833391.4 KARE K1353 SF3987.2KD832231.4 MEAKE K1332 IF4987.7RP832231.2 LEAOS K1329 SF2787.7KD362619....
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48 views

Disk utilization on mdadm raid 5 is 100% even though none of the member disks is at 100%

I am currently confused about the disk utilisation of one of my machines. The setup: I have a machine containing 4 2TB HDDs. For those HDDs I used mdadm to configure a RAID 5 (called md2) On MD2, I ...
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31 views

Performance issues on internal SATA device causing high load

I have a problem with the performance of my laptop. In fact I needed to install quite some things recently and the whole machine froze from time to time completely. First some general information: I ...
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2answers
222 views

USB speed bottlenecks (specifically while running virtual machine)

This question is mostly about USB performance on Linux, but more specifically performance issues when running virtualbox images off of my USB. I posted this on the virtualbox forum, but so far no one ...
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79 views

Context Switching or High runqueue , who is the culprit?

I have an application which uses nio threads for which I have configured same maxthreads and minspare threads ( tomcat ) . Now when the I hit with Load for a longer duration I observed sudden ...
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1answer
58 views

How can I copy and verify a file as I do the copy?

(Yet another "copy and verify" question...) I have a reasonable amount of data I want to copy between several HDDs, and I want to make absolutely sure the data is copied correctly. My current ...
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330 views

ubuntu 18.04 - too long to show login

it takes on average 2 minutes showing the splash screen before the login widget is made visible. blame did not show anything suspicious (this is after removing splash and quiet optiona off in grub): ...
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53 views

is there any way to increase spawn rate of MinSpareServers in apache prefork

My server faces huge traffic only for short duration every day. And I don't want to waste my resource by running high amount of MaxSpareServers throughout the day. So, I would like to know is there ...
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41 views

How can I find the deepest and most stack-hungry call chains in a program?

I have a program written in OCaml that tends to stack-overflow on platforms with small stacks. Rather than ulimiting the program to find and solve stack overflows one by one, I'd like to get a sorted ...
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32 views

PMU and tracepoints

I am searching for information about the mechanism of creation of tracepoints. From this topic What are Kernel PMU event-s in perf_events list? and this blog brendangregg I've got that tracepoints are ...
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202 views

journalctl's mmap() calls make it incredibly slow

Whenever I run journalctl, it runs astonishingly slowly. It often takes minutes or even hours to return results. I've experienced some other performance problems on the affected machine that seemed to ...
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47 views

CUDA on Linux - screen freezes

So I have Fedora 27 and I have installed the latest NVidia drivers on a laptop that has a Quadro M1000M. I am trying out an intense CUDA process (xmrig). But when it's running, the graphical screen ...
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1answer
400 views

How to deal with blocking I/O reducing the performance to a crawl?

I have a computer which is experiencing some serious I/O issues. Software: Kali-rolling, Linux x86-desktop-1 4.12.0-kali2-amd64 #1 SMP Debian 4.12.13-1kali2 (2017-10-03) x86_64 GNU/Linux. But I've ...
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100 views

NMVe SSD Fedora Throughput Tests too High

I am testing throughput of a Samsung 950 Pro SSD Card which uses NVMe protocol. My current method of testing is to mount a file system on a partition and write a file of size X bytes to the file ...
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391 views

If cpu frequency scaling is not supported, server will run at max performance?

SERVER413:~ # modprobe acpi_cpufreq FATAL: Error inserting acpi_cpufreq (/lib/modules/3.0.101-108.13-default/kernel/drivers/cpufreq/acpi-cpufreq.ko): Input/output error SERVER413:~ # In the BIOS, all ...
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1answer
313 views

How can I improve Firefox performance?

I just "upgraded" to Firefox 57, the holy grail of alleged performance perks, yada yada. Im not here to complain that it breaks all the add ons. My problem is that the response time for IO is ...
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153 views

C++ code runs 3-fold faster on Linux mint 17.1 vs Linux 18.2

I run C++ code (consisting of differential equations and solvers etc.) on two Linux mint versions. First tried with Mint 18.2, which spent 17 minutes to finish the job. Then Mint 17.1 was installed to ...
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232 views

How to find evidence of performance issues caused by too many threads on linux

We have a RHEL 5 server, with 16 CPU cores, that runs a number of Java processes that get batch jobs submitted to them. Each java process has about 80 threads that are used to process these jobs. ...
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1answer
163 views

How do you specify a blkparse format specifier that also suppresses summary

When using the live mode, I do: blktrace -d /dev/sdc1 -o -|blkparse -f '%a %c' -i - I just want to limit the displayed data to 'action' and 'cpu id'. Instead I get the summary and all the usual ...
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643 views

High iowait while the throughput and IOPS are low

I'm new to programming & Linux. After I finished my programs(do some IO), I found iowait is very high(~65%) while the throughput(~5M/s read + ~5M/s write) and IOPS(50~100 QPS) are low. iostat -...
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19 views

Measuring speed of communications between processes

Ubuntu 16.04 I have 2 processes which communicate between each other. The process p1 writes data to stdout, the process p2 in turn reads this data and does some processing. The issue is it is all ...
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74 views

Relation between write and filesystem blocksize in SSD disks on Apple

R. Stevens, in his famous book about programming in O.S. environment, taught us that when the syscall write's block size is comparable (or even equal) to the filesystem block size, the performances ...
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2answers
1k views

Fedora 25 Running Slow After Software Update

I've been running Fedora 25 on my machine for a couple weeks now. I happened to shut down the machine, and there were some software updates that automatically installed. After booting the next time ...
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23 views

Keep an amount of ressources for virtual console (Ctrl + Alt + Fx)

Sometimes, a process on my computer uses a lot of RAM, and ends up using the SWAP. Therefore, my computer becomes extremely buggy, and I can't even toggle a terminal or a virtual console to kill the ...
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174 views

iptables: does making use of -m conntrack increase system load?

Lets compare these two rulesets iptables -i lo -j ACCEPT and iptables -i lo -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT iptables -i lo -j LOG Obviously they differ in how they treat ctstate=...
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143 views

Fedora behaves sluggish after the upgrade 24 → 25

I have upgraded my Fedora installation from 24 to 25. Since then, things that were done instantly before sometimes take half a second now. Examples are: Switching the workspace in Awesome WM Typing ...
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1answer
502 views

Why is dig query time slower on one computer vs another in the same LAN?

To make a long story short, I setup DNS forwarding/caching using dnsmasq built into my router (EdgeRouter). My test command is simple: dig www.example.com On one computer, which happens to be a ...
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220 views

Larger number of context switches for kondemand

According to the documents on the web, kondemand is responsible as cpu scaling governor. kondemand is a kernel thread that belongs to the ondemand governor of cpufreq subsystem, which changes the ...
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55 views

multiple directories for sar command

Is it normal for below directories created by sar command -rw-r--r-- 1 root root 348948 Nov 3 23:50 sa03 -rw-r--r-- 1 root root 348757 Nov 3 23:53 sar03 -rw-r--r-- 1 root root 348948 Nov 4 23:50 ...
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191 views

Does dstat captures disk i/o by the OS prefetching?

I ran a program which sequentially reads a big file. The transfer rate [MB/sec] is strictly controlled by the application as 5MB/sec. However, when I monitored the disk i/o bandwidth usage using ...
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550 views

Discrepancy between shared memory from /proc/meminfo and ipcs

Running free -hm outputs: total used free shared buffers cached Mem: 15G 15G 389M 321M 169M 11G -/+ buffers/cache: ...
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360 views

LVM mirror creates high load from time to time, how to lower these effects?

Or: How to throttle down one LVM mirror leg lowering its assumed synchronization cpu load? Is it possible to tweak a LVM mirror configuration so it takes it easy on mirroring files? Whenever there ...
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1answer
784 views

HTML5 video performance

I have performance problem with video playing: When I am playing video on youtube, high CPU percentage is used: But when I download the same video and play it in VLC player, CPU usage is reduced ...
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89 views

Performance problem Fedora 23 32-bit @ Dell D630 4GB/Nvidia

I have installed Fedora 23 32-bit at Dell D630 4GB with NVidia Quattro NVS 135M (nvidia.ko, not nouveau.ko). And I have permanent performance problem as X-Windows (Gnome) are very slow and laggy. I ...
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1answer
462 views

How to monitor system performance over time

I wrote the below script to determine how my system is holding up against various games. It checks all the vitals (GPU, RAM, and CPU) and then appends the data to a log file. Is this a reasonable ...
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965 views

Why my server cannot serve more than 400 concurrent connections

I have an Ubuntu 14.04 LTS, kernel 3.13 in a Intel Xeon + 8Gb box. It has apache 2.4.7 configured in mpm worker with up to 4000 workers. The max bandwidth allowed by the ISP is 100Mbps. If I test ...
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1answer
217 views

Fast filesystem for virtual backup environments

I know filesystem supporters war is behind the corner and there are plenty of fine tuning guide for each filesystem in the wild, so please stick to the specifications: I'm asking what would you ...
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2answers
680 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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2answers
524 views

What 4.2 Kernel Optimizations could I make to speed up CR48 netbook?

I have a CR48, had one for years. Love the little gremlin, but it is still a single core machine with the chances of upgrading the processor being slim and none (Even then what looks to be the best ...
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121 views

Adding a second GPU greatly reduces my graphics performance

I'm currently running Ubuntu 15 desktop with an ATI R9 390 and a 4k monitor via display port. Everything runs smoothly. I have a second monitor which is VGA-only, and since the R9 has no VGA ports, ...