The speed at which a program runs

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Poor hard disk read perfomance, but not with O_DIRECT

Since a few days my vps, which supposedly mounts a SSD disk, has been showing a very poor disk read performance. For example, with hdparm -t I get numbers around 20MB/s, while hdparm -t --direct shows ...
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1answer
33 views

Find process that stalls apache

I'm programming a PHP web page and I started seeing some strange behavior on my computer, at some point apache / php takes to long to show the webpage on the browser (8 secs), first i thought it was ...
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3answers
94 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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52 views

Why does flood ping to localhost result in lower RTT's?

I used ping to do an estimate of lower bound for HTTP request times as part of a feasibility study. In order to make the test faster I lowered the interval of the ping (to get enough pings to get a ...
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2answers
28 views

What tools can I use to diagnose the exact reason for laptop slowness? And how do I use those tools?

I am running Linux Mint 17 on my laptop. When using applications (mainly Web Browsers) the machine freezes for little time periods. The CPU indicates 100% usage at such times, but this only seems to ...
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1answer
334 views

How to find what is hammering my I/O?

On a Ubuntu Linux machine that is used as a webserver, I see that I'm really hammering the I/O: - dysphoria():~$ iostat -d 3 3 Linux 3.13.0-45-generic (dysphoria) 2015-10-20 _x86_64_ ...
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2answers
61 views

does anybody know of a GNU/Linux project which has support for both gcc as well as clang?

Does anybody know of a project (apart from the Linux monolithic kernel) where a/the program can be compiled by both the compilers and can be used to observe their performances, any recommendations ? ...
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1answer
38 views

How to trace program execution?

Currently go program 1.3, 1.4 and 1.5 has a really different compilation performance, the later has about 4x slower than the former. How to trace the go compiler execution? something like this: ...
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2answers
59 views

Getting filename based on filehandle number

I am running strace -p 1234 -o strace.out on a system where process it is suspected that process 1234 is performing badly. I see these reads that take almost a minute to complete: read(11, ...
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85 views

system user + kernel time using /proc/stat

user: normal processes executing in user mode nice: niced processes executing in user mode system: processes executing in kernel mode idle: twiddling thumbs iowait: waiting for I/O to complete irq: ...
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57 views

issues with acpi-cpufreq and frequency scaling

I am using the Ubuntu distribution on Intel(R) Core(TM) i7-2760QM CPU @ 2.40GHz with Kernel version: 3.14.5. I deactivated the intel_pstate driver and activated the acpi-cpufreq driver with userspace ...
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1answer
85 views

What is the effect of smaller pages?

Does a smaller page size lead to smaller page table(s)? If so, is that good or bad !? I think that this lead to more data handling. Is it possible: to test that within Linux manually or that ...
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91 views

turbostat - how to tune to make CPU%c1 = 100

I'm using my server for low-latency trading. I'm using Low Latency Performance Tuning for Red Hat Enterprise Linux 7. It suggests to run turbostat sleep 5 command to verify that Bzy_MHz = TSC_MHz, ...
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1answer
85 views

Wanted: nonassociative array in AWK

I am looking at speeding up some code in AWK by serially processing an internal string representation instead of serially processing an array representation. (For Examples 1 and 2 below assume ...
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1answer
102 views

What's the fastest way of writing 1s to a hard disk? [duplicate]

I'm currently writing 1s to a file using the following: tr '\0' '\377' < /dev/zero > /dev/sdb But this is a really slow method when I want to fill a 500GB disk. Is there a quicker way?
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218 views

Very high I/O wait time on KVM virtual machine

Debian wheezy AMD64, 3 cores, 2560mb ram (virtual machine). 1 virtual drive on ext4, running on KVM. I decided to move it from raw to qcow2. Everything is ok and everything was going ok during ...
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39 views

Find system idle time using any system call in microseconds

For the perf analysis and to make decision based on system and app performance I need to find the idle time of system. I want the precise value in microseconds. I know that I can get the value in ...
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3answers
82 views

Rebuild original file from diff files to save disk space

Every day 10GB text file is downloaded, the file is ~200 million lines and ~1% of the lines are changed the next day. I want to keep daily files as backup, but I'm trying to save disk space by using ...
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35 views

Install orca on redhat

Has anyone successfully installed/ran orca (a performance monitoring tool for Solaris) on Redhat? I see some old posts asking about it but there have been no responses. ...
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0answers
22 views

Calculate the correct MBit/s in my speedtest

I know wget is usually showing the speed in a summary. But in my small OpenWRT shell, I want to test how long it takes to download 100MB with t=$(date +"%s") wget ...
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2answers
354 views

Fastest way to delete duplicates in large wordlist?

I need to deduplicate a large wordlist. I tried several commands and did some research here and here where they explain that the fastest way to deduplicate a wordlist seems to be using awk. awk ...
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1answer
159 views

How low can I go on RAM?

I have some old PCs runnning on my business. And by old I mean PENTIUM-3 800 MHZ and AMD DURON 950 MHZ, with 256MB RAM. They are running my business software today on Windows XP. I want to run Linux ...
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150 views

How does performance measurement tool 'perf' actually work?

perf is a tool which accesses the performance counter registers of an machine and gives out metrics to user to analyze the system performance. What I am curious about is, when I read the parts of ...
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1answer
90 views

Python processes appearing and disappearing in top

I concurrently launched around 12 Python scripts on a 24-core server (Ubuntu 14.04 LTS x64). Each of Python script takes around one hour to complete. I see in top that they appear quite sporadically, ...
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2answers
938 views

Why I can not use all the 100% potential of CPU?

I am using my computer clusters to run a MD C program but I can not use full potential of those clusters. But the this node have 16 CPUs and I also only give 15 jobs for those CPUs. But I can not ...
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3answers
325 views

Grep all at once

The script I have receives arguments and needs to grep through another file. Script loops through every argument. Is there a way to collect the arguments in a single search string and grep with OR ? ...
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0answers
59 views

How can writing speed equal to reading's over nbd and ram disk

My testing is under two nodes whose communication is over nbd,and each node uses ram disk as local storage.The result is that reading speed can reach the bandwidth 6GB/s,while writing speed is only ...
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2answers
326 views

how to go mouseless [closed]

I would like to improve my efficiency. I recall seeing some tool to use gui applications on linux with the keyboard, but I do not recall much else about it! Please advise how I can go mouseless(for ...
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3answers
339 views

The performance difference between a command that does the same thing

What is the difference? It is performed in the same? tar -czf files/compressed/gzip/archive.tar.gz -C files/original . tar -c -C files/original . | gzip -1 > files/compressed/gzip/archive.tar.gz ...
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1answer
185 views

how to disable access time settings in Debian linux

Performance Best Practices for MongoDB implies that: Most file systems will maintain metadata for the last time a file was accessed. While this may be useful for some applications, in a ...
3
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1answer
55 views

Cache atime writes

Is there a way to set atime writes to be cached for a very long time? I need atime (that is to say, relatime won't cut it), but I don't want it to effect performance so much. Data loss in of atimes ...
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3answers
393 views

Linux, SSD and swap

This article suggests not to create a swap space on an SSD drive in order to reduce its wear. On the other hand, it suggested here that swap space positively affects performance. Would it be a better ...
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1answer
214 views

btrfs on LVM on LUKS - one LUKS container performs WAY better than the other

I have 2 LUKS containers, one with default OpenSUSE installer settings, another one with -h sha512 -s 512 -i 5000 and detached header. On top of each of them there is LVM - one with only 1 OS volume ...
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233 views

where to compress=lzo, btrfs with virtual disk images, with their vm's internally using btrfs

I've been using compress=lzo on my btrfs volumes, because I read this fast compression method actually increases drive performance. (Haven't tested myself.) I'm starting to use ...
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1answer
49 views

Is it possible to have some shared objects be preloaded asynchronously during boot?

If I recall correctly, the same shared object is not loaded into memory twice when it's used by multiple processes. Is it possible to have some shared objects preloaded into memory asynchronously ...
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1answer
184 views

Wordlist/dictionary generation for penetration testing

How can I generate a dictionary of words containing 8-16 of alphabet characters ([a-zA-Z]) with low memory?
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12 views

Turn off slide effect on kde menu

I have a remote computer via a nomachine connection. I use kde on the remote machine. How to turn off slide effect in KDE menu?
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1answer
92 views

Stable timing for shell scripts?

The run times of scripts vary quite much. I would like to find similar time -function as Matlab's timeit, described here. For instance, I am evaluating these commands here about counting quickly ...
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1answer
65 views

How can I track long-term system performance in Linux (Debian)?

I love the RRD graphs that pfSense provides. Is there a package for Debian or a generic tool that can do the same for my Debian box?
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47 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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2answers
221 views

Performance of `tar -xf` (block size related)

I'm recently working on optimizing the performance of tar -xf, i.e. untar a file. I notice that under default settings, tar -xf calls writes to write 10 KiB output at a time in chunks. However, this ...
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1answer
225 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: ...
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1answer
164 views

What is the impact on system performance when kernel debug info is enabled?

In order to debug kernel or use tools like stap (https://en.wikipedia.org/wiki/SystemTap) kernel must be compiled with full debugging information included - namely option CONFIG_DEBUG_INFO has to be ...
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1answer
341 views

Show CPU core usage for parent process and its child processes

Is it possible to display CPU core usage just for a single process and its child processes on Linux?
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3answers
623 views

Linux & Linux-Software: Advantages of a multi core processor [closed]

I plan to get a new notebook and try to find out if a quad-core processor gives me any advantages over a regular dual-core machine. I use common Linux Distributions (Ubuntu, Arch etc.) and mostly ...
0
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1answer
81 views

Relaunch an app if it freezes

Yesterday I successfully managed to make a kiosk from Ubuntu Server. I'm going to use it to rub some web application that will run non-stop. However, in some cases, duo to lot of js animation I'm ...
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1answer
356 views

Least resource-consuming Linux OS to run just Chrome

I've developed some application which uses a browser in order to run. The usage of the browser is simply for the GUI which is built with html/css/js (there are lot of js animations). Currently, the ...
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2answers
222 views

What is actually the speed reported by dd?

I always thought that when doing: dd if=/dev/sdx of=/dev/sdy the report which is displayed once the command finishes, such as: 79304319+0 records in 79304319+0 records out 40603811328 bytes (41 ...
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765 views

Linux Mint 17.1 Cinnamon is slower in computer than in Virtual Box

After some months working in a VirtualBox VM with Linux Mint (the host as a Windows 7), I've finally installed Mint 17.1 Cinnamon on the same computer. And the experience hasn't been good. The fact ...
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2k views

How to calculate the memory consumed by a “C” program in linux

I have written two C programmes one is using function pointer, and the other without function pointer. Now i want to know the memory consumed by the two programmes , to see how memory can ...