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3
votes
2answers
648 views

What is the expected performance of obnam? Or: why is it so slow?

I've been playing around with obnam these last few days, and although it looks very promising and seems to offer basically everything I ever wanted in a backup tool, I am pretty disappointed in its ...
38
votes
2answers
46k views

How do you empty the buffers and cache on a Linux system?

Prior to doing some benchmarking work how would one free up the memory (RAM) that the Linux Kernel is consuming for its buffers and cache?
2
votes
2answers
43 views

Why is userspace slower than the kernel?

I've heard that FUSE-based filesystems are notoriously slow because they are implemented in a userspace program. What is it about userspace that is slower than the kernel?
5
votes
1answer
34 views

How to find the number of bytes rewritten to a folder hierarchy?

I want metrics for how much writing and reading have been done to a folder. vmstat -d gives metrics at the whole disk level. iotop will give per process rw stats. But how can I find out how much ...
0
votes
1answer
17 views

Where is NMon cron job for AIX?

While trying to know where is NMon job configured to run; I do find that it's NOT listed on Crontab (using crontab -l). BUT - the job is currently running as expected, which is weird. See the ...
0
votes
1answer
522 views

NFS server optimization for maximum performance

I'm looking for maximum of performance for a NFS mount. I'm on local network, it could be completly unsecure, the performance is the most important in my case. What I already found : In /etc/export ...
2
votes
4answers
924 views

Why is writing SLOW on raw device, and FAST on filesystem (USB key)?

I have a USB key (PQI U822V-Speedy 32G) that I am trying to benchmark quick'n'dirty on Linux. I'm testing write bandwith. dd on raw partition I created a partition starting at sector 2048, then did ...
1
vote
0answers
5 views

Is inode_readahead_blks independent of read_ahead_kb?

I've been reading through the kernel documentation for block device sysfs tunables and I ran across the description for read_ahead_kb: Maximum number of kilobytes to read-ahead for filesystems on ...
1
vote
1answer
47 views

Is it useful for a proxy to buffer less data than Linux RCVBUF can?

I am looking at how HTTP proxies and reverse proxies deal with slow client problems. The idea is that the upstream server only have a limited slots for clients and if the client is slow to receive ...
1
vote
0answers
25 views

Why does my fresh Debian have a high latency?

The time between clicking and seeing a response is very high. Typing looks very funny, and makes me feel queasy. I think there's about 50-20ms "extra". I would expect a top notch linux distro to have ...
3
votes
1answer
36 views

How does netstat command fit in various layers of TCP/IP model in the performance diagram?

netstat command is useful to, Print network connections, routing tables, interface statistics, masquerade connections, and multicast memberships. Now, I was reading about the Linux performance ...
0
votes
0answers
40 views

Increasing ulimit stack size benefits?

Hello I'm new in Linux and at my work I have a server that runs a banking software. The company that made the software said that the stack size should be set to unlimited. Does this make the software ...
0
votes
1answer
414 views

How do I create a RAM disk on Linux Mint?

I am running a package that adds data to the end of 140–300 files each time through the process. I'm thinking of moving the process to a RAM disk, and using rsync to copy it back when done. My goal ...
21
votes
11answers
8k views

the lightest way to have a GUI in Linux? [closed]

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 ...
2
votes
1answer
27 views

Why is my computer sluggish after downloading a lot?

When I download a lot of data (e.g. 3GB) in one go, using a program such as Transmission or Wget, progressively during the downloading, and after it has has finished, the computer always seems ...
1
vote
0answers
31 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 ...
4
votes
2answers
84 views

Disk busy is close to 100% and iowait is 0,0% on SunOS, how can it be possible?

During monitoring of SunOS5.10 machine I noticed strange behavior: Disk busy is close to 100% Disk waiting time is 0,0% Primary purpose of this machine is running application server on jvm. This ...
0
votes
2answers
2k 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 a ...
16
votes
3answers
1k views

Why is coreutils sort slower than Python?

I wrote the following script to test the speed of Python's sort functionality: from sys import stdin, stdout lines = list(stdin) lines.sort() stdout.writelines(lines) I then compared this to the ...
4
votes
1answer
1k views

Audio/video out of sync when playing MP4s in mplayer

When I try to play MP4 files in mplayer, after a few seconds I get the "Your system is too SLOW to play this!" warning and the video starts lagging behind the audio. It only happens with MP4s, and ...
2
votes
1answer
46 views

What could be done to make Embedded Linux boot faster?

My team is developing a software for a Embedded Linux solution. The problem we are facing is that it takes too much time for the system to be ready to start running our desired apps (that is, too much ...
1
vote
1answer
52 views

why doesn't iozone generate output file?

I'm using iozone3 for tesing, on Xamin (an Debian-based OS). When I enter iozone command, for example iozone -Rab output.xls, the test runs successfully. But after running the test (after displaying ...
0
votes
1answer
58 views

rsync: Copy speed decreases while syncing two directories

I am using rsync on fedora 20 to sync my directories. I am using the command below:- $ rsync --progress -a srcDir DestDir But, as rsync copies files, copy speed decreases significantly. Here is my ...
0
votes
0answers
22 views

Xorg consumes CPU, RHEL 7 fresh install

I've installed RHEL 7 with default settings. I wonder why Xorg consumes 30% of my CPUs. How can I know what's wrong and how to fix it? HP DL360p Gen8, dual Xeon E5-2640
3
votes
2answers
27 views

Optimize file layout for minimal seek in specific situations

Starting VLC is slow on my system. The reason: it reads more than 1000 different .so files. Is there a way to make it read those files faster? I think if all the files followed immediately after each ...
1
vote
0answers
27 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 ...
1
vote
1answer
94 views

Find the process which is taking maximum CPU usage if CPU usage is more than 60%?

I am trying to measure the cpu usage of my ubuntu machine and if the cpu usage is more than 60%, then I need to find out the process who has the highest cpu usage and then send out an email saying CPU ...
1
vote
1answer
34 views

Disk is a bottleneck. Background processes make things worse. How to improve responsiveness?

Often, the bottleneck of my laptop is the disk. When doing some disk-intensive computations, automatically-started background processes like updatedb, find /something etc. kick in, making things even ...
1
vote
3answers
35 views

Software RAID10 setup writes small files extremely slowly, is this normal?

I have a software RAID-10 setup on Linux 3.16.6-203.fc20.x86_64, with 1.2 metadata and the default chunk size (512K): $ cat /proc/mdstat md0 : active raid10 sdc1[4] sdb1[0] sdd1[2] sde1[3] ...
2
votes
1answer
106 views

How to test Disk IO on VMs with iozone?

I want to test the disk IO performance like read, write, random read, random write and so on both in physical machine and VMs (with aufs file system). Also I want to test the throughput performance in ...
6
votes
3answers
1k views

Transfering millions of files from one server to another

I have two servers. One of them has 15 million text files (about 40 GB). I am trying to transfer them to another server. I considered zipping them and transferring the archive. But I realized that ...
0
votes
2answers
8k views

CPU usage monitoring in AIX servers

In order to monitor the CPU usage in an AIX server I'm using the following script that is executed every 10 mins. lparstat 2 10 > cpu usage=$(tail -10 cpu | awk 'BEGIN {sum=0;} {sum+=$4} END{print ...
0
votes
1answer
50 views

Questions about CPU usage [closed]

How bad/normal/good is this CPU usage? Cpu0 : 14.4%us, 6.3%sy, 0.0%ni, 78.8%id, 0.0%wa, 0.0%hi, 0.5%si, 0.0%st Cpu1 : 88.3%us, 8.0%sy, 0.0%ni, 0.0%id, 0.0%wa, 0.0%hi, 3.7%si, 0.0%st ...
0
votes
2answers
666 views

Authentication very slow (both with ssh and su)

I'm having a problem on one of our production servers where the login attempts become progressively slower as time passes. After roughly 5 days it becomes so slow that some critical processes/cron ...
0
votes
1answer
32 views

Why scp with compression takes longer than without compression

I was playing around and noticed that secure-copying with compression takes longer than without compression time scp -C ./test.sql user@vmware:/home/user real 0m42.758s user 0m40.455s sys ...
0
votes
2answers
42 views

won't the ever changing affinity assigned to threads by the Linux kernel have adverse effect on overall performance?

In my program, I have several threads that are started with the process and that remain until the program ends. They will meet different loads during the lifetime of the app, and at times they will ...
3
votes
1answer
97 views

Why is ImageMagick's `compare` command so slow and is there an alternative?

I have a shell script running on an little Atom based Micro-ATX box that is doing some watchdog-like functions for a number of devices on a local network. One of the things it's doing is monitoring ...
4
votes
1answer
2k views

Very high CPU load, but nothing significant in top

I'm running Ubuntu Linux 12.04.1, with VirtualMin 4.08.gpl GPL and 2 CPU cores. Pretty much all the time for the last few weeks, it's been running at well above load average of 5, usually up closer ...
22
votes
4answers
2k views

How to limit resource usage to save CPU+RAM for a certain process?

I have a dev server on which sshd sometimes stops working because the machine runs out of RAM. Yes we are running low on memory and upgrading is not a feasible choice right now. What I want to do is ...
4
votes
1answer
250 views

How accurate is Conky?

I'm on Crunchbang 64 bit, Conky shows that I'm using 4% of my CPU. But I can feel the CPU burning so hot, got Spotify, Chrome and couple other apps running. On windows 7 chrome uses about half of the ...
4
votes
2answers
596 views

Why load is high despite the fact that neither CPU or disk is overused

I'm getting the following output from top: Cpu(s): 43.8%us, 32.5%sy, 4.8%ni, 2.0%id, 15.6%wa, 0.2%hi, 1.2%si, 0.0%st Mem: 16331504k total, 15759412k used, 572092k free, 4575980k buffers ...
6
votes
1answer
128 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 ...
22
votes
7answers
6k views

Force directory to always be in cache

I've been testing out different methods to improve the time it takes to compile my entire c++ project. Currently it takes ~5 minutes. I experimented with distcc, ccache, and others. Recently, I ...
1
vote
0answers
21 views

What tools can show me the CPU usage that doesn't appear in top/sar?

I have a virtual machine that's using ip_tables to set up some connection forwarding. According to top, sar and /proc/stat, I'm > 99% idle. However, perf says I'm only about 72% idle, with the rest ...
18
votes
4answers
2k views

Is there a fastest way to shutdown the system?

Or is shutdown -h now the fastest it can get? I look for some syscall or similar that will allow to skip lots of the stuff done prior to shutdown (in particular to care about the running proccesses). ...
1
vote
1answer
72 views

Why does mouse and keyboard freeze when Linux swaps

I have noticed that under Linux, when there is heavy swapping, the mouse cursor freezes, and even CapsLock or Ctrl+Alt+F1 don't work. The system uses the deadline I/O scheduler but this should not ...
26
votes
4answers
2k views

python vs bc in evaluating 6^6^6

I am evaluating the expression 6^6^6 using python and bc separately. The content of the python file is print 6**6**6. When I execute time python test.py, I get the output as real 0m0.067s ...
1
vote
3answers
99 views

Why does find -inum iterate through the whole filesystem tree?

It surprises me to see find iterate/walk through the complete filesystem when I do a simple find -inum 12345 Without background info it seems to me that there should be much easier ways for to tell ...
1
vote
2answers
51 views

Increasing performance of clear text file reads

In our bioinformatics application we have large files (up to 900MB, typically 100MB). These files contain a clear text representation of a genome, and are essentially a 1 line file with a sequence of ...
1
vote
0answers
15 views

Many transient files on journaled filesystem?

Writing and deleting many files quickly I'm going to write many temporary files per second, over a sustained period. Each will be deleted after some milliseconds. Say we have an image processing ...