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1
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0answers
13 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
0answers
28 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 ...
17
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
38 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
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2answers
42 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
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0answers
8 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
21 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
1answer
22 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
59 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
1answer
19 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
33 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
46 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
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0answers
13 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
62 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
30 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
42 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
34 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
21 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
93 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
49 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
61 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
47 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
70 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
48 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
30 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
35 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
113 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
187 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 ...
2
votes
1answer
705 views

How much speed difference for a tweaked bios versus uefi boot? [closed]

EFI can be faster, but that's not certain. The biggest speed difference is in hardware initialization early in the process. On my systems, this is a fraction of the total boot time, so a ...
0
votes
2answers
263 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
0answers
71 views

Ubuntu 13.10 x64 - slow and acting strangely gvfs+NTFS

I have updated Ubuntu 13.10 x64 to latest stable releases of all packages. I'm running GNOME and using SSD disks on USB 3.0 ports in lenovo Y500 notebook. I'm using Midnight Commander (as root) in ...
0
votes
1answer
75 views

Lower cpu performance in Linux [closed]

I have a problem with my CPU performance in Linux. I have a laptop, Toshiba Satellite C660-101. Despite the fact that the CPU works perfectly fine in Windows 7, Linux has some serious issues. ...
0
votes
1answer
44 views

RAID Level 5 versus Level 1

Is it slower to write one block in RAID Level 5 with 5 disks than RAID 1 with two disks (mirroring only)? I think No since with Level 5 you are writing the data and the parity (two writes). With Level ...
2
votes
2answers
71 views

Will grep go faster with line breaks?

I have some big files that I have changed into "standardized form", removing line breaks. I want to speed up greps on those files. I know that you can optimize grep by doing grep 'partofpattern' | ...
17
votes
2answers
767 views

Is dash or some other shell “faster” than bash?

I always thought that the only benefit of using dash instead of bash was that dash was smaller, and therefore many instances of dash would start faster at boot time. But I have done some research, ...
7
votes
2answers
494 views

Why is `tac file | grep foo' (piping) faster than `grep foo < <(tac file)' (process substitution)?

This question was motivated by "Reverse grepping", about grepping a huge file from bottom up. @chaos said: tac file | grep whatever Or a bit more effective: grep whatever < <(tac file) ...
0
votes
0answers
26 views

Can ramdisk improve performance when stats show low wait and system cpu use?

I have jobs that do I/O of rates peaking around 200mb/s. On high load (over twice cpu cores) I tried to copy large file and got only few mb/s. Gathered dstat show single digits in wai and sys category ...
3
votes
1answer
71 views

Artificially prime buffer cache?

Is it beneficial to artificially prime the buffer cache when dealing with larger files? Here's a scenario: A large file needs to be processed, line by line. Conceptually, it is easy to parallelize ...
6
votes
2answers
175 views

Reduce bad block retry / wait times in Ubuntu

How can I reduce the IO wait time and retry times so that the OS doesn't continually try to write to a failing drive? I have an system that I use to make copies of demo content that gets loaned out ...
1
vote
0answers
12 views

Ubuntu with LAMP+Mediawiki suffering spikes

I'm sorry if this question is off topic, but I'll give it a shot: I have a VPS running Ubuntu 12.04, a LAMP stack, and Mediawiki. After installing Mediawiki I noticed that my wiki site was spiking, ...
1
vote
1answer
55 views

Slow Linux machine [closed]

Every time I login (via ssh) in my Linux/debian computer it takes too long for the password prompt to appear. Also, every time I try to run a python script or a tcpdump it takes too long until it ...
9
votes
1answer
93 views

Limit on the number of btrfs snapshots?

I am considering using btrfs on my data drive so that I can use snapper, or something like snapper, to take time based snapshots. I believe this will let me browse old versions of my data. This would ...
2
votes
0answers
48 views

Cgroups - memory subsystem

I want to set the memory.limit_in_bytes parameter for a control group and disable OOM, so processes freeze when the limit is reached. But i want to change that limit dynamically, if there is more ...
3
votes
2answers
84 views

Testing the Success of a Congestion Algorithm

How do you test whether a particular congestion algorithm is working for you? I ask because it's not as if I can easily re-create a representative workload for most algorithms. I'm current looking at ...
1
vote
1answer
54 views

apache mod_security and performance

I have a list of bots to block, so I was thinking that fail2ban could be a solution until I realized that mod_security would be more efficient in this kind of tasks. The number of bots is huge, so ...
0
votes
0answers
46 views

OTG musb and full speed bulk endpoint throughput

We are developing an application on an OMAP3 device (DM3730 ti). An acquisition board gets samples and sends them to the OMAP board via USB. This acquisition board does a 16KHz sampling which ...
3
votes
3answers
95 views

Advantages to uploading files to /tmp before moving off to permanent storage?

It seems the common trend in programming when building functionality for handling file uploads is to have the file first uploaded to a temporary directory/folder (e.g. /tmp on Linux). Once the file ...
4
votes
1answer
133 views

Does ionice work with the deadline scheduler?

My Debian Wheezy systems use the deadline scheduler. I'm accustomed to using ionice to reschedule the I/O priority of disk-intensive jobs at busy times, and anecdotally this seems to help (but I ...
1
vote
0answers
60 views

Do kernel threads seem to interfere with full tickless mode?

I'm trying to disable local timer interrupts for low latency. I have full tickless mode enabled in the kernel config and I have the boot parameter nohz_full set for the cores in question. However ...
2
votes
1answer
938 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 ...