The speed at which a program runs

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92 views

string fill performance in shell scripts: what is the best amount and for what shell?

I was trying to determine the best performance for string fill like in: str+="A" #one per loop I came with this script for bash: #!/bin/bash bReport=false nLimit=${1-3000}; #up to 25000 echo ...
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43 views

How can I prevent my browser from hogging all system resources?

I'm using a laptop, with a reasonable (though not stellar) CPU and memory. I run Lubuntu 15.10 on it, to be resource-conservative. Still, when I have a browser - specifically, Mozilla Firefox, but I'm ...
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36 views

LVM Logical Volume (linear) best performance

As a system administrator, one thing I do very often is increase LV's size. In most cases I have to extend first the VG, adding a new disk (we are talking about virtual machines). I have got a lot of ...
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1answer
46 views

sed: multiple ranges between patterns, with one pass

I have a script that reads a file of about 3GB and sends it through a pipeline involving a very small number of replacements in a very small part of the file. To accomplish this with minimal overhead, ...
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0answers
131 views

Reducing Number of MariaDB/MySQL Threads

So I'm running a MariaDB 10 database on a single core server; not super powerful, but then my needs aren't huge either. However, one thing I've noticed is that if I look in htop I have around 28 ...
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1answer
394 views

Check if partitions are aligned properly for performance?

I just created a GPT disk label for the entire space on my hard disk (/dev/sda) like so: # parted (parted) select /dev/sda (parted) mklabel gpt Warning: The existing disk label on /dev/sda will be ...
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2answers
34 views

How to find out contention

I'm looking for an easy tool, to graphically show the amount of resources being used realtime. Something like htop but with disk IO, memory and network usage as well. I tried ganglia and the fact ...
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18 views

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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122 views

Debugging Slow Queries in MariaDB/MySQL

I've set up a MariaDB server and everything is running well, with most queries executing in well under 20 milliseconds, but every so often a query will take half a second or longer (sometimes several ...
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48 views

spstack, ptrace stopped a process

My server is busy with sys CPU, so I used pstrace to trace it but no output, so I cancel the command inside putty, and then use pstack to trace it again, but no result return either and I closed the ...
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2answers
71 views

how to delete larger file (e.g., 180G) in unix system?

Because of some reasons, my server machines had some too-large files (e.g.,:180G), How can I delete these files quickly?
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63 views

Linux huge IOPS difference - same disks

I've been investigating for some time regarding some IOPS issues I've been experiencing.. And my mind is getting crazy! I have two servers (one bought 2 weeks ago, another 1.5 years ago) that I ...
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0answers
45 views

Is “top” accounting for Kernel Interrupts?

I have a simple interrupt that is triggered by a GPIO-input. The IRQ only increments a variable and returns. When I turn the frequency of the interrupts up to somewhere around 10-20 kHz, the system ...
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2answers
337 views

How to call bash function from within awk?

This is a bit tricky; I'm trying to work out the best approach to this problem. I have a couple of approaches, but they seem really hacky and I'd like something a little more elegant. I want to ...
0
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1answer
24 views

How can I improve performance using a system remotely via SSH?

I know I can use compression with the flag -C. Any other ideas? Also, besides my internet connection (which I think is fairly fast), what could be causing the network to slow down?
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27 views

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 ...
2
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1answer
34 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
102 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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59 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 ...
2
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2answers
30 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 ...
2
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1answer
340 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
62 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
40 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
64 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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98 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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65 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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111 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
87 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
103 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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253 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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42 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
85 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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36 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
23 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
367 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
162 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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161 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
106 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
981 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
327 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
61 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
358 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
341 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
219 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
60 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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446 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
234 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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251 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
52 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 ...