Questions tagged [performance]

The speed at which a program runs

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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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224 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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789 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
551 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, ...
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What can interrupt execution of threads which are pinned to cores?

I do low-latency application development and I use isocpu and set thread affinity to reduce (eliminate?) context switching during my critical threads. However, I am unsure what other types of ...
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115 views

Apache's sudden drop of requests

My server was working fine until a couple of weeks ago. All of a sudden, I started getting error notices from PHP. Lost connection to MySQL server at 'reading authorization packet', system error: 0 ...
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3answers
3k views

CPU > 80% - how can I debug?

I am running a laravel application on a Ubuntu 14.04 digital ocean vps and I am using New Relic to monitor the server. I got an email alert that my CPU usage was above 80%. I logged in to New Relic ...
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115 views

multiple daemon running for the same service in RHEL6

I am using RHEL6.6 on VM. ControlMinder(CA) is installed there. Some of the vms I saw multiple seosd processes running. It causes high cpu usages by sys (using top) and decrease the performance of os ...
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186 views

How can I profile/benchmark RAM performance?

I would like to know if my memory hardware is a bottleneck of my system performance. I am dealing with really old hardware (late 2000). If there is room for improvement, I would like to upgrade. ...
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1answer
1k views

Why is my UDP bandwidth significantly lower than TCP bandwidth in iperf

I am running a simple bandwidth test between two VMs using iperf. I am getting very different bandwidth reading for TCP and UDP where the UDP bandwidth is terribly lower than TCP. TCP: root@i-sahmed-...
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305 views

Disk configuration options, what can affect performance

I have 2 disks, the same model and vendor, first one , probably performs faster. We do write into multiple files. Can you compare 2 configurations and tell what can affect performance? 1. (faster) *-...
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Is the perfmon2 tool obsolete due to the same functionality being included in the current Linux kernel?

I was having some issues with the PAPI tool and multiplex and this answer by the PAPI creator led me to check out perfmon2: http://lists.eecs.utk.edu/pipermail/ptools-perfapi/2008-April/000900.html ...
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619 views

'nc' using ~100% CPU when transferring a FIFO file

On the server which is always connected I’m using this in a crontab: @reboot nc -k -l 1337 < /tmp/fifo.fifo On the client which is not always on the network or switched on I’m using this command: ...
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225 views

Variations in Ubuntu 12.04 /usr/bin/time statistics

I have a command line tool which I run on Ubuntu 12.04.5 LTS. I need to calculate the cpu time for this program. I have been checking /usr/bin/time function. command: /usr/bin/time -v -a -o ...
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621 views

How to diagnose CPU performance problems?

Recently I bought a new netbook based on AMD A4-1200 CPU and installed Linux Mint 17 with XFCE. RAM is 4GB So, testing some of my programs, I found very strange behavior. On random intervals, the ...
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430 views

Properly mount a windows share to move files on the mountpoint

This question resulted from a question of mine on stackexchange. I mount a windows share with mount -t cifs -o username=username,password=password,rw,nounix,iocharset=utf8,file_mode=0777,dir_mode=...
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How fast is a process reading/writing virtual memory?

We have top, htop, iotop, iostat, vmstat, etc, to measure many different things on Linux, but how can one measure how much MB/s a process is reading and writing to/from RAM, i.e., virtual memory?
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87 views

How can we measure performance overhead resulting from writing to files or folders?

I have a tool which takes as input a folder or a file and then it logs operations done on that file or folder (modifying,deletion,creating new folders or files, etc). I was looking for a way to ...
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670 views

Horrible Iceweasel and Opera performance when watching youtube

I have 64-bit Debian on laptop with Intel Core 2 Duo T9300 2.5GHz, Nvidia Quadro NVS140M GPU and 4GB RAM. For now - im on vacation and im using 3G USB modem. I have relatively slow but high quality ...
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116 views

Ubuntu with LAMP+Mediawiki suffering spikes

I'm sorry if this question is off topic, but I'll give it a shot: I have a VPS running Ubuntu 12.04, a LAMP stack, and Mediawiki. After installing Mediawiki I noticed that my wiki site was spiking, i....
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2answers
444 views

apache mod_security and performance

I have a list of bots to block, so I was thinking that fail2ban could be a solution until I realized that mod_security would be more efficient in this kind of tasks. The number of bots is huge, so ...
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Monitoring Disk Latency

We have quite a few physical machines in our environment, yet we have no trending data over a period of time for disk latency statistics. We can easily run the standard iostat commands to see what the ...
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58 views

Amount of memory transfer on a running Linux

Can I determinate the amount of RAM exchange (between the CPU and the RAM) on a running Linux system? I'm not looking for the max RAM speed (then memtest would be valid answer). I'm looking for the ...
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79 views

memory consumption alert

My VPS has reported a memory consumption alert says reached 273% and I cannot access any of my sites. But I checked on the terminal today and it does not look like a memory problem. Am I correct in ...
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505 views

Why does my CMS run extremely slow in my workstation (Ubuntu)

For over a year I have been struggling with the response speed on my Drupal v7.2x CMS install. Let me explain. I'm running Drupal 7.2x on an Ubuntu 12.10 (upgrade to 13.xx pending) for the purpose of ...
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606 views

X high CPU when using Java applications

Only recently, my Freemind program has become extremely sluggish and unresponsive (big lag) when moving my mind map around. I use Arch Linux with xfce4. Freemind is made with Java. If I move the mind ...
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1answer
40 views

Order of magnitude of when vmstat's swap si/so must be considered unhealthy?

With vmstat I can see in the swap si/so columns how many blocks are read/written from/to the swap per second. I have a system with tight memory and therefore need to make use of the swap. Which is ...
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hugepagesz page table questions

trying to understand linux page tables... I am reading the RHEL 7 performance tuning guide and watching youtube vid of RH summit may 2018 https://www.youtube.com/watch?v=RLNMlsa173o* Having System H ...
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Image processing time shows periodic peaks

I have an ARM64 single-board computer with RK3399 CPU running Ubuntu 18. I wrote a Python script that acquires images from a USB camera and feeds them to a Caffe neural network. I measured the ...
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performance monitoring of “iptables” kernel module

I woul dlike to know, how much CPU / memory my current iptables rules consume. I tried looking in ps and htop, but even with kernel threads displayed, I don't see anything related to iptables. How ...
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RHEL CentOS 7 cpu performance tuning

On a shared memory 4 socket server having ~512GB DDR4 RAM or greater and greater than 64 cores running Intel xeon cpu's, taking any disk I/O out of the equation by doing systemctl enable tmp.mount and ...
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1answer
28 views

Measure startup times of tmux

I'd like to profile the performance of tmux. In particular how fast starting up a session is (and maybe also attaching to a session). I'm especially interested in how the content of my .tmux.conf file ...
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15 views

Is there a way to artificially slow down Apache http server transactions to simulate load?

Is there a way to artificially slow down Apache http server transactions to simulate load? I'd need to force http transactions to take 100ms+ instead of the normal 3ms, without killing the CPU or ...
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32 views

Playing video is slow via XPRA

When using XPRA within a home-sized LAN, I find that the speed is a bit slow. Playing a video is like slowly playing a sequence of slides. How can I make XPRA faster or shall I use some other software?...
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Multithreaded xz, with gzip, pv, and pipes - is this the most efficient I can get?

I'm excited to learn that xz now supports multithreading: xz --threads=0 But now I want to utilise this as much as possible. For example, to recompress gzips as xz: gzip -d -k -c myfile.gz | pv | ...
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cryptmount performance for large partitions?

Has anyone tried cryptmount with a large amount of data, say, several terabytes? Looks like a filesystem is stored in a single user disk file (such as ~/crypto.fs), so it makes me wonder if it can ...
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29 views

Software RAID slows down while emptying buffer

I am experimenting with mdraid in CentOS 7.6, trying to understand these results from fio. I am doing a sequential write to a 4 stripe array, and the speed starts out good while it writes to the RAM ...
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What is 0.dylib.opt in linux

I'm running a multi-threaded server on a linux machine with 40 cores. The program has some serious bottlenecks since I cannot get the CPU utilization above 30% no matter how much load IO give it. The ...
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24 views

Server performance jitter after reboot

We are experiencing a strange linux server performance jitter problem: one of our app's P999 curves show that there exist severe jitter on some of our linux servers, while other linux servers don't ...
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How to make Linux GUI faster?

Background (skip the following paragraph if you want to jump straight to the question): I'm a web developer, and have been using Windows since the beginning of my career. Over the years though, my ...
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RBP 3B+ horrible Kodi performance

I've tried a lot tips and tricks to get Kodi to work properly on my RBP 3b+ but so far, no luck. Maybe someone here recognises this issue and knows how to tackle it. setup: RBP 3B+ with the ...
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Large file processing performance

I did a simple performance test of csv processing a while ago, and want to share results with community, maybe you can point out, what test could be more precise and fair. Firstly i took out 42 MB ...
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49 views

Debian bootchart2

I try to enable bootchart on debian to collect performance metric and build graphics. I follow this guid. The following approaches doesn't work for me: When system reboot press e and append command ...
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18 views

Rebinding many keys at once

My goal is to have a very accessible way to remap many different keys. More specifically I want the number row and the home row to swap positions on my keyboard when I press shift+space. Right now I ...
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How we can get performance metrics from VTune in command line of Linux?

I am going to record all performance metrics mentioned https://software.intel.com/en-us/vtune-amplifier-help-cpu-metrics-reference by using VTune in command line for my C++ code. I used $ amplxe-cl -...
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Can perf events detect deadlock in C++ codes (Linux)?

I am using perf tools to get some performance counters. I would like to know if it is possible to detect deadlock by checking performance counters included in perf events.
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Want to capture host metrics for 60 min in every 3 sec through nmon

I want to run nmon for 60 min which will collect the host metrics in every 3sec. And to achieve this I run the below query on my host, nmon -ft -s 3 -c 60 /home/Documents/nmon When I analyze the ...
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What are the performance overheads between logging in to another user account via ssh vs login

In Gnu/linux systems, I can perform a full local login (i.e. where logname returns the same output as whoami) by two methods: login: sudo login second_user (prompted for password) ssh: ssh ...
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19 views

Huge hdd usage while gaming

For testing I tried to run Path of Exile and Guild Wars 2 on Ubuntu Budgie and Mint XFCE. To run PoE I used steam. To run GW2 I used Lutris. When any game is fully loaded and I do not touch anithing ...