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2
votes
2answers
40 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
33 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
14 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 ...
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
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
33 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 ...
1
vote
1answer
46 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 ...
0
votes
0answers
39 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 ...
2
votes
1answer
26 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
80 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 ...
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 ...
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 ...
0
votes
0answers
21 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
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 ...
1
vote
1answer
91 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] ...
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 ...
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
1answer
49 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
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 ...
1
vote
0answers
20 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 ...
3
votes
1answer
95 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 ...
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
70 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 ...
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 ...
1
vote
1answer
81 views

How to measure iptables load?

I have added about 3500 IP addresses to iptables using ufw on a Debian 7 and I am wondering if this has any impact on the performance of my server. How can I measure that?
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
3answers
97 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 ...
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 ...
0
votes
0answers
43 views

Powerful Workstation

I heard about ILM's (Industrial Light and Magic) workstations on which they create models and scenes for a lot of different movies. They have workstations with more than 1024 GB of ram and a lot of ...
2
votes
0answers
74 views

Why adding swap space is the slowest part of the booting process? [closed]

I'm not having performance problems, but just running dmesg command, I can see that adding Swap space is the slowest part of the booting process. Why? I actually have ~4GB for swap and 2GB RAM ...
0
votes
0answers
20 views

Pentium D and GeForce 6700 does not have enough power to play DVD full screen

I have an older computer which I would like to use as a DVD and video file player. These are the specs: CPU = Intel Pentrium D @ 3 GHz RAM = 1 GB GPU = NVIDIA GeForce 6700 XL HDD = 229 GB OS = Ubuntu ...
0
votes
1answer
82 views

What's the pros and cons of disabling the swap partition if the RAM is large enough? [duplicate]

My computer has 16GB RAM and 1TB SSD. So I think the swap partition is not needful. What's the pros and cons of disabling the swap partition if the RAM is large enough? Is it recommended to disable ...
1
vote
1answer
42 views

benefits of huge pages on a laptop/desktop

I have read about huge pages and its the (potential) benefits. However, I am still confused whether this is mostly beneficial on a server with lots of RAM, or if it can be advantageous on a ...
4
votes
1answer
61 views

Printing to an X terminal faster than printing to tty?

In Linux Mint 17, I was testing the printing speed of the default ttys versus the speed of a mate-terminal running on Xorg. To test the speeds, I generated a random file: dd if=/dev/urandom ...
2
votes
0answers
50 views

Help troubleshoot a very slow system performance (Kubuntu, intel graphics) [closed]

As the title says the performance of my laptop is simply terrible. i3 M380 @ 2.53GHz, 4GB RAM (of which more than 2GB is rarely used), intel HD graphics (to external monitor through HDMI). It takes ...
0
votes
0answers
23 views

How can we measure performance overhead resulting from writing to files or folders?

I have a tool which takes as input a folder or a file and then it logs operations done on that file or folder (modifying,deletion,creating new folders or files, etc). I was looking for a way to ...
6
votes
2answers
106 views

How come sed is so fast?

I thought about whether this question is suitable for SE or not, I hope you agree it is. Some time ago I asked on SE how to find text in files and leave the file with only the matching lines that ...
1
vote
0answers
119 views

Horrible Iceweasel and Opera performance when watching youtube

I have 64-bit Debian on laptop with Intel Core 2 Duo T9300 2.5GHz, Nvidia Quadro NVS140M GPU and 4GB RAM. For now - im on vacation and im using 3G USB modem. I have relatively slow but high quality ...
2
votes
3answers
106 views

Is cmp faster than diff -q?

In a recent AU question on checking whether some files have differing content, I saw a comment stating that if the differing sections didn't matter, cmp would be faster than diff. This SO answer ...
1
vote
1answer
88 views

blktrace - differentiating between sequential to random io

I'm looking for a way to determine whether an app is doing sequential or random I/O. Is it possible to look at a blktrace capture and say if I/O is sequential or random? If yes, any examples of what ...
2
votes
1answer
105 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 ...
1
vote
2answers
63 views

Is it bad to have too many Kernel modules?

I'm trying to compile a Linux kernel to debug an issue I have on Arch Linux, and I was configuring modules, but I didn't know what a lot of the stuff was so I left them on. If this kernel works I ...
0
votes
0answers
66 views

Why would attempts to bind affinities for rcu kthreads fail?

I am trying to get full tickless mode working on my box on Ubuntu kernel 3.10.39. I am running the following command: for i in `pgrep rcu` ; do taskset -pc 0 $i ; done It seems to work on some of ...
1
vote
1answer
50 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
3answers
603 views

dd write vs read performance

I have recently done some performance tests on a new server (using dd) and wonder why read performance is so much worse than write performance? Shouldn't it be another way around? file size was in ...
4
votes
6answers
231 views

grep with a lot of files which contains a lot of lines?

Imagine we have a lot of huge(30000 line)files: a.2014-05-06, a.2014-05-07, a.2014-05-08 and so on. I know that we can grep a line with word using this command: grep "word" a.* First I guess this ...