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4
votes
5answers
375 views

performance monitoring

Is there some performace monitoring tool which would run in background gathering info about all system activity? Somethimes my system (Arch linux, 32 bit) slows down terribly and the top utility ...
0
votes
1answer
204 views

Samba daemon hammering CPU on CentOS 5.6 VM on bootup

I have a problem where my Centos 5.6 VM is running very slow on my Win7 machine, and looking at top I can see that the Samba daemon smbd is sitting at the top of the list hitting the CPU big time, ...
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?
3
votes
1answer
62 views
+50

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 ...
3
votes
3answers
757 views

slow media - disk cache tuning?

Is there any way to make the system more consistent when using LUKS? (or slow storage in general) as it is everything is snappy until the write buffer is full, then everything grinds to a halt as the ...
-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/ ...
6
votes
2answers
635 views

Poor random read SSD performance on Linux

I recently got an Intel 320-series SSD, and I am having difficulty achieving the advertised 38K IOPS for random 4K reads. Both with fio and my own hacked-together program, I am seeing around 6K IOPS. ...
37
votes
5answers
17k views

Can I configure my Linux system for more aggressive file system caching?

I am neither concerned about RAM usage (as I've got enough) nor about losing data in case of an accidental shut-down (as my power is backed, the system is reliable and the data are not critical). But ...
6
votes
3answers
573 views

How to average time commands?

I am timeing some of my commands. Now to average the measures, I'd like to run and time my commands a specified number of times, and get the results with a calculated mean and standard deviation. The ...
2
votes
4answers
103 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
76 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 ...
1
vote
1answer
167 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 ...
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 ...
0
votes
2answers
413 views

Ubuntu is running slow

I'm not sure since when it became slow, but I think after I did apt-get update. Here's my machine details: I can see from the system monitor that the CPU is working hard specially when I run Chrome ...
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
75 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 ...
4
votes
1answer
307 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 ...
0
votes
1answer
178 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): ...
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
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 ...
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 ...
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 ...
14
votes
5answers
6k views

Is there a parallel file archiver (like tar)?

Is there something out there for parallel archiving of files? Tar is great, but I don't use tape archives, and it's more important to me that the archiving happens quickly (with compression 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 ...
8
votes
7answers
2k views

Processor usage increases with 4GB RAM installed

I have an Intel Atom D2700 (Synology NAS DS412+) with 4GB RAM running kernel 3.2.30 x86_64. This unit has a single DIMM slot. One thing I, and other's have found, is that when adding a 4GB DIMM ...
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 ...
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 ...
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 ...
3
votes
2answers
782 views

Is it possible to trigger OOM-killer on forced swapping?

Is it possible to have the system preemptively swap out inactive pages (vm.swappiness), but invoke the oom-killer when the system runs out of RAM (as opposed to running out of memory) and is forced to ...
8
votes
4answers
8k views

Why is kworker consuming so many resources on Linux 3.0.0-12-server?

Last Friday I upgraded my Ubuntu server to 11.10, which now runs with a 3.0.0-12-server kernel. Since then the overall performance has dropped dramatically. Before the upgrade the system load was ...
4
votes
2answers
230 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 ...
20
votes
11answers
6k views

the lightest way to have a GUI in Linux?

I have been using Gnome and KDE for a while, and I am now running Compiz standalone... Regarding system resource, I think the most heavy ones are feature-rich desktop environments (Gnome, KDE), then ...
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 ...
2
votes
5answers
995 views

How to determine why a machine is running slowly?

I log into a linux server (installed as a virtual machine) using a graphical ssh client (securessh). This server runs a tomcat5.5 server where nexus is installed. When I type commands or delete/copy ...
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 ...
0
votes
2answers
1k views

Console CPU utilisation chart

I need to monitor CPU and network utilisation from a terminal. For network traffic, I have found the perfect tool: slurm It gives me a moving chart. It gives me an nCurses-like UI I can use from ...
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
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 ...
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 ...
1
vote
1answer
552 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& ...
1
vote
2answers
989 views

Opensuse 11.4 very slow on 8 GB RAM i5 processor

EDIT : This is when top is run with "M" . Snapshot when Eclipse starts ( using "iotop") Snapshot when Eclipse building workspace After Eclipse has done its thing Its as slow as before ...
3
votes
2answers
239 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
62 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 ...
3
votes
6answers
692 views

How can I defragment my SSD on linux?

This page demonstrates that defragmentation is beneficial for SSDs. I suppose this type of defragmentation has to be trim-aware, so as to preserve the life time of the disk. How can I do that on ...