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0
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0answers
12 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
87 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
18 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
44 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
32 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
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0answers
54 views

Why iperf still reports 1Gbps performance when using bonding over two 1Gbps adapters? [migrated]

As I understand it, bonding brings among other benefits the ability to increase the network speed between two machines in a LAN. Bonding [...] means combining several network interfaces (NICs) to ...
2
votes
1answer
34 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 ...
0
votes
0answers
16 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
23 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
53 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
159 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
191 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
98 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
42 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
70 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
40 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
68 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' | ...
15
votes
2answers
407 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
462 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
21 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
62 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
137 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
11 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
73 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
40 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
73 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
39 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
42 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
83 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 ...
3
votes
0answers
72 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
46 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
379 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
142 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 ...
8
votes
3answers
1k 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: ...
1
vote
2answers
219 views

Very poor read performance compared to write performance on md(raid1) / crypt(luks) / lvm

I'm experiencing very poor read performance over raid1/crypt/lvm. In the same time, write speeds are about 2x+ faster on the same setup. On another raid1 setup on the same machine I get normal read ...
0
votes
0answers
31 views

If a buggy application underperforms, it it possible server tuning could have no affect?

To set the stage, imagine if you will: A read-heavy Tomcat Application with MySQL on Red Hat Enterprise Linux with some problematic Java Class files which resulted in the application performing a ...
1
vote
0answers
79 views

Monitoring Disk Latency

We have quite a few physical machines in our environment, yet we have no trending data over a period of time for disk latency statistics. We can easily run the standard iostat commands to see what the ...
3
votes
2answers
305 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 ...
1
vote
1answer
145 views

CPU Placement in KVM

I have a configuration of KVM guests where the cpu placement is configured as follows: <vcpu placement='static'>1</vcpu> Now since I don't have a cpuset specified I was reading libvirt ...
0
votes
1answer
134 views

Is it useful to setup RAID0 on laptop? [closed]

I have a Dell laptop, which I am going to replace the CD-ROM hub with a HDD. I am thinking if I setup a RAID0 on my original HDD and the new HDD, would I have some I/O performance improvement? ...
1
vote
1answer
48 views

How does downloading speed vary between download managers? [closed]

I used several download managers on Ubuntu and found variation in downloading speed. uGet (recommended) Flareget xdm (Xtreme Download Manager) Steadyflow I find variation in downloading speed. My ...
3
votes
1answer
110 views

Performance differences between pipelines and process substitution

I tend to use pipelines in my bash scripts over process substitution in most situations, especially in cases of using multiple sets of commands as it seems more readable to do ... | ... | ... over ... ...
2
votes
1answer
126 views

speed up linux server [closed]

On my VPS, I have centOS 6.5 installed with 2 virtual cpu 2048 MB memory, 60 GB disk and 300 GB monthly data. Doing a speed test today resulted in 168.62 Mbit/s dload and 37.39 Mbit/s upload. Then my ...
3
votes
2answers
357 views

Large ext4 partition ridiculously slow when writing

We have four identical Linux servers with a large (5T) hard disk partition. We have Scientific Linux with this kernel: Linux s3.law.di.unimi.it 2.6.32-358.18.1.el6.x86_64 #1 SMP Tue Aug 27 14:23:09 ...
1
vote
0answers
45 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/ ...
3
votes
2answers
185 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?
2
votes
4answers
419 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 ...
5
votes
1answer
178 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 ...
3
votes
1answer
379 views

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 ...