The speed at which a program runs

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3
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1answer
793 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
3k 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). ...
3
votes
1answer
445 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
68 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 ...
3
votes
1answer
74 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 ...
3
votes
1answer
1k 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
38 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
2answers
521 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
507 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
1answer
150 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
571 views

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

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 memory. dione@saturno:~$ dmesg | grep -C 4 swap [ 2.179979] input: ...
0
votes
1answer
280 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
135 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 laptop/...
5
votes
1answer
171 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 of=...
2
votes
0answers
178 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 ...
1
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0answers
61 views

How fast is a process reading/writing virtual memory?

We have top, htop, iotop, iostat, vmstat, etc, to measure many different things on Linux, but how can one measure how much MB/s a process is reading and writing to/from RAM, i.e., virtual memory?
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0answers
38 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
450 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
561 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 ...
3
votes
3answers
1k views

Is cmp faster than diff -q?

In a recent Ask Ubuntu 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 Stack ...
1
vote
1answer
845 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 ...
-1
votes
1answer
93 views

Why doesn't rsync take advantage of the mv command when --remove-source-files is specified?

Assume I want to move a tree in the filesystem, e.g. /path/to/a a.txt b.txt to another location with rsync (3.0.9 protocol version 30), e.g. with rsync -a --remove-source-files /path/to/a/ /...
2
votes
1answer
1k 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 ...
2
votes
2answers
204 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 ...
2
votes
1answer
439 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
9k 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
343 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 ...
4
votes
1answer
18k 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 reduction ...
1
vote
3answers
5k 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
180 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
79 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
146 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' | ...
27
votes
3answers
7k 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
1k 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) ...
37
votes
4answers
6k views

Reverse grepping

Let's say, I have a really big text file (about 10.000.000 lines). I need to grep it from the end and save result to a file. What's the most efficient way to accomplish task?
3
votes
1answer
155 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 ...
7
votes
2answers
2k 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
112 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, i....
1
vote
1answer
138 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 ...
14
votes
1answer
1k 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
116 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
142 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
228 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 ...
2
votes
3answers
499 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 ...
8
votes
1answer
1k 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 don'...
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0answers
249 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 ...
8
votes
1answer
18k 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 ...
0
votes
1answer
2k 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 ...
12
votes
3answers
15k views

What are the exact differences between awk and cut with grep? [closed]

We know that we can get the second column of the line we want from a file using these two techniques: awk '/WORD/ { print $2 }' filename or grep WORD filename| cut -f 2 -d ' ' My questions are: ...