The tag has no wiki summary.

learn more… | top users | synonyms

-1
votes
0answers
22 views

Good book for tuning/optimizing Linux? [closed]

I am looking for a good book to learn how to optimize/tune Linux, which also explains how/why the recommendations makes the kernel perform faster. I did find this book, Optimizing Linux Performance: ...
1
vote
0answers
12 views

is star faster than GNU and BSD tar? [closed]

I made serveral runs (create a tarball) on OS X Mavericks with BSD tar, GNU tar and star. star is always the winner. System is iMac (Mid 2010) only running Terminal. root@time var> du -sh log/ ...
3
votes
2answers
102 views

How to record the actual running time of a program with other programs running? [duplicate]

When timing the wall time performance of an OpenMP program on Linux while other programs are running, how can I get the actual running time?
2
votes
4answers
104 views

Why is dd so slow on raw device, so fast on filesystem (writing on USB key)?

I have a USB key that I am trying to benchmark quick'n'dirty on Linux. dd on raw partition I'm testing write bandwith. I created a partition starting at sector 2048, then did a 4 GB sequential ...
5
votes
1answer
77 views

Attempting to Abbreviate kSAR's PDF output

I'm currently writing a cronjob around kSar's command line (non-GUI) options in order generate PDF's. I'm just going to email a PDF of the previous day's activity to a different webmaster (basically ...
3
votes
1answer
65 views

RFC 2544 / Y1564 software implementation

Is there any RFC 2544 and/or Y1564 software available for Linux? I'm aware that tools like iperf, bw-ng and bmon exist, but I was not able to find something that mimics Ethernet tester functionality ...
12
votes
1answer
921 views

Why is my TCP throughput much greater than UDP throughput?

I haven't done anything unusual to my hardware or kernel configurations (all default settings, fresh OS install, Linux kernel 3.11 TCP/IP stack) and I'm averaging about 3.83 million messages per ...
1
vote
1answer
169 views

High performance routing with high churn ruleset. What approach is most likely to scale to C10K and beyond?

I've been asked to create a high throughput router using PC / server hardware. I'm modestly familiar with pf, iptables, and tc, but I've never had such high churn and so many rules. I hope you can ...
22
votes
5answers
2k views

Why is iterating over a file twice faster than reading it into memory and computing twice?

I'm comparing the following tail -n 1000000 stdout.log | grep '"success": true' | wc -l tail -n 1000000 stdout.log | grep '"success": false' | wc -l with the following log=$(tail -n 1000000 ...
1
vote
1answer
76 views

Can we make grep faster by indexing words in files? [duplicate]

Over a decade ago I imagined an improved version of grep that would use indexes to make recursive searching faster. I never got around to writing it, but I wonder if somebody else did! My original ...
34
votes
1answer
1k views

Diagram of Linux kernel vs. performance tools?

Is there a diagram that shows how the various performance tools such as ip, netstat, perf, top, ps, etc. interact with the various subsystems within the Linux kernel?
6
votes
1answer
82 views

Do processes in cgroups have to be set every boot? If so, how to persist them?

I was reading this answer to a question on setting limits for processes by using cgroups. The sample given sets limits for a process (in the example, sshd). In the answer, the PID of the process is ...
6
votes
7answers
456 views

Make disk/disk copy slower

Is there a method of slowing down the copy process on Linux? I have a big file, say 10GB, and I'd like to copy it to another directory, but I don't want to copy it with full speed. Let's say I'd like ...
2
votes
3answers
57 views

How to optimize this oneliner? (if second column empty, put the line in another file)

I have a little "oneliner": while read ONELINE; do if [[ -n "`echo $ONELINE | awk '{print $2}'`" ]]; then echo "$ONELINE" >> LIST-ok.txt else echo "$ONELINE" >> ...
2
votes
1answer
87 views

Analyse the performance of an rsync command from FreeNAS to a USB drive

I infrequently run a task where I rsync my photos (~30 directories with 10-100 files in each) from my FreeNAS machine to an external USB hard drive (500GB WD) as a redundant backup. I execute the ...
3
votes
3answers
164 views

Can I just disable updatedb?

Is updatedb necessary at all? I never use locate and my servers tend to have dozens of millions of files which usually makes updatedb to run for a long time and consume I/O needed by MySQL and/or ...
0
votes
1answer
179 views

What is the effect of rsync --block-size on large files?

I want to backup a few terabytes of large files (500mb to 1500mb each) to a backup server (BULK storage) via rsync. For this I use the following command (updated with suggestions from @Gilles): ...
1
vote
0answers
13 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 ...
1
vote
1answer
51 views

How to measure the time a packet spends on the system(router)?

I have a streaming system and one if its components is a router/firewall. I'm using iptables for setting the required behaviour on the router. I'm having performance issues in forms of a constant ...
4
votes
2answers
232 views

Why is dd using direct slower writing to disk than to a file

I am trying to compare aggregate write rates when writing to a file in a GPFS file system, as compared to writing directly to a disk on a system with Red Hat Enterprise Linux Server release 6.4 ...
1
vote
0answers
32 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 ...
3
votes
1answer
112 views

CPU is free, yet bash script not utilizing all CPU resources

I ran a simple script to generate a large (10000000 lines) csv file with 6 fields in which some fields changed in each line/row, using a while loop. The machine had all (32) CPUs free, lot of RAM (~31 ...
2
votes
1answer
115 views

What is the most accurate way to measure disk read/write speed for an OpenVZ VPS host from within the host itself?

CentOS 6.x | OpenVZ I have an openvz VPS host and would like to measure disk read/write speed. Historically, on other physical systems, I've ran hdparm to collect this information. I haven't been ...
2
votes
1answer
81 views

Does negative vs positive matching impact firewall performance?

I am curious if using negative vs. positive matching impacts the performance of the netfilter stack. e.g. is iptables -I INPUT -p tcp -s 192.168.0.0/16 -j DROP equivalent to iptables -I INPUT -p tcp ...
0
votes
1answer
69 views

ERROR: cube viewer is not available!

I have installed and configured the following: cube-4.2.1 opari2-1.1.1 papi-5.2.0 scalasca-2.0 scorep-1.2.1 I am trying to run scalasca -examine, but I get the following error: ERROR: cube viewer ...
4
votes
1answer
308 views

Why is rm slow?

I have been trying to use rsnapshot for making backups, but I'm finding it unusable. While it is able to diff a directory (50gb) and duplicate it (hardlinking every file) in a few minutes, and I can ...
3
votes
2answers
240 views

Basic sed command on large one-line file: couldn't re-allocate memory

I have a 250 MB text file, all in one line. In this file I want to replace a characters with b characters: sed -e "s/a/b/g" < one-line-250-mb.txt It fails with: sed: couldn't re-allocate ...
7
votes
2answers
47 views

How can other processes affect measurements made with `time`?

If I time a process using the time command, I get output for 'real', 'user', and 'sys'. My understanding from this discussion is that 'real' is wall time, whereas 'user' and 'sys' are process time. ...
1
vote
1answer
62 views

Performance of RAID 1 with 3 Disks under Linux

The standard way to setup a RAID 1 under Linux is to use two disks of the same size. The write performance is almost as good as with a single disk drive. The read performance can be up to twice the ...
1
vote
0answers
63 views

Solaris 10 on x86: local sockets (unix domain sockets) very very slow? [closed]

I'm writing an application both on Linux and Solaris 10. It uses local sockets for some internal communications. On Linux an open, exchange one short message & close cycle takes about 10us elapsed ...
0
votes
2answers
36 views

Fedora 17 Performance Issues [closed]

I have a Dell Latitude E4310. I have Windows 7 and Fedora installed on it. I rarely use windows and I have been using fedora for a good 9 months now. Recently the performance on my machine degraded ...
1
vote
1answer
553 views

Running thousands of curl background processes in parallel in bash script

I am running thounsand of curl background processes in parallel in the following bash script START=$(date +%s) for i in {1..100000} do curl -s "http://some_url_here/"$i > $i.txt& ...
3
votes
4answers
200 views

Does cron jobs per se represent a significant burden on a modern system?

I'd like to run a pretty simple script (is there a dir with name x in dir y if so move it to dir z–and x will only be there about once a day) every 15 seconds or so (one minute divided into 4*15 ...
2
votes
1answer
41 views

Multiple Lan interfaces on one VM rather than multiple VM

I'm looking if it's possible to give rights, to only allow the use of one network interface to a specific user on a Linux distribution. My use case: I want, for my studies, testing the ...
1
vote
2answers
53 views

Varing speed when reading sequentially from a HDD

I have just got a new HDD and I wanted to test the sequential read speed (the whole disk). I used: pv /dev/sda > /dev/null The disk is 500GB WD VelociRaptor (WD5000HHTZ). At the beginning the ...
0
votes
1answer
156 views

Performance Issue: AWS Medium Linux Instance V/S Hetzner Dedicated Instance

I am testing an AWS Medium Instance with CentOS (AWS AMI) and comparing it with Hetzner's EX40-SSD (http://www.hetzner.de/hosting/produkte_rootserver/ex40ssd). Software setup on both is comparable( ...
23
votes
9answers
860 views

for vs find in Bash

When looping through files there are two ways: 1. use a for-loop for f in *; do echo "$f" done 2. use find find * -prune | while read f; do echo "$f" done Assuming these two loops will ...
1
vote
1answer
139 views

Ubuntu 12.04LTS becoms slow and jerky randomly for a mintue and then becomes normal by itself [closed]

I am using Ubuntu 12.04LTS on my Toshiba satellite L510 and I have only Ubuntu installed. The system becomes slow and jerky by itself after every 10minutes or so and the remains like that for less ...
9
votes
2answers
608 views

Why is wc so slow?

Why is the wc utility so slow? When I run it on a large file, it takes about 20 times longer than md5sum: MyDesktop:/tmp$ dd if=/dev/zero bs=1024k count=1024 of=/tmp/bigfile 1024+0 records in 1024+0 ...
3
votes
3answers
142 views

Best way to benchmark different encryption solutions on my system

I want to compare different encryption solutions for encrypting my system, possibly different solutions for different parts of the system such as /usr or /home. In particular I look at dm-crypt ...
3
votes
1answer
165 views

Efficient way to print lines from a massive file using awk, sed, or something else?

If I had a plain-text file containing 8 million lines and I want to print out lines 4,000,010 to 4,000,000 to the screen, which would be more efficient: awk or sed? There is no pattern to the text, ...
2
votes
2answers
254 views

Massive, unpredictable I/O performance drop in Linux

I'm using Debian testing without any problems for ~6 years (I'm just regularly updating it), but recently it started to show a random behaviour that can be summarized as "Low I/O performance which ...
1
vote
0answers
72 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 ...
4
votes
2answers
2k views

Benchmark ssd on linux: How to measure the same things as crystaldiskmark does in windows

I want to benchmark a ssd (possibly with encrypted filesystems) and compare it to benchmarks done by crystaldiskmark on windows. So how can I measure approximately the same things as ...
3
votes
1answer
167 views

Rsnapshot via SSH speed issue

I am trying to backup bunch of desktops running RedHat 6.4 (i86_64) LVM on the top of ext4 to our file server running RedHat using rsnapshot and ssh. I am on 1GbE. I am finding the speed of the first ...
1
vote
0answers
62 views

Terraria Server Seems to be Slowing Down Web Server [closed]

I currently have a CentOS 6 Cloud server (2gigs of ram, 40gigs of SSD storage, 2.4ghz quad core, and 100M unmetered port for bandwidth) that has in the past run a TeamSpeak, Minecraft FTB (modded ...
4
votes
3answers
253 views

Why is bash's printf faster than /usr/bin/printf?

I have two ways of calling printf on my system: $ type -a printf printf is a shell builtin printf is /usr/bin/printf $ file /usr/bin/printf /usr/bin/printf: ELF 64-bit LSB executable, x86-64, ...
1
vote
2answers
138 views

Performance and limitations of using an X GUI remotely?

I don't really have any experience with X. It appears from what I read that X has always been built from the ground up to allow windows in the WM to be transmitting over the internet, without ...
0
votes
1answer
241 views

How can I install perf 3.4.25?

By installing perf using sudo apt-get install linux-tools-common sudo apt-get install linux-tools-3.2.0.23 gave me perf version 3.2.14 How can I install perf 3.4.25? Is it related to kernel ...
0
votes
0answers
161 views

How can I figure out the reason of the lagging of Cinnamon?

So I am using Mint 15 with Cinnamon on my Dell XPS L502x (Sandy Bridge i7 + 8G + GTX540M + 300G SSD). I am using Numix theme and a custom font. I installed Bumblebee, but I am not using nVidia card in ...