The speed at which a program runs

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1answer
37 views

How to deal with high number of page faults?

I've got ~200000 page faults per second and I think it's a huge number and it affects the overall system performance. I'm using MBP with 16G of RAM. How to deal with such number of page faults (...
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2answers
22k 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 ...
4
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0answers
19 views

How does ionice work with multiple drives?

I understand how ionice can help you when you have multiple processes requesting access to the same disk resources, but how does it work when you have multiple disks? For example, you have one rsync ...
2
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4answers
4k 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 ...
2
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1answer
24 views

performance comparison of multiple commands excutions

I've got three different programs written in three different languages, and I'm trying to compare their performance in terms of runtime, and memory consumption. What I'm looking for is some command ...
3
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0answers
12 views

Keyboard slowing mouse refresh rate under Debian 8

This odd issue is preventing me from developing software on my current Debian Jessie setup. Whenever I press or hold a key on the keyboard – any key with the apparent exception of shift and alt&...
3
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0answers
58 views

Performance Optimization

I have one script which roughly has to read 1.5 million lines and process the lines and print out output in cvs file. This script is current taking more than 8-9 hours to process 250 thousands lines. ...
7
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4answers
3k 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 ...
0
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1answer
42 views

storage performance test [closed]

So we have some operational Red-hat Linux on physical servers and company are we decided to migrate them to VM's. I wonder if they have same performance on writing and reading from disks. they are ...
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2answers
1k views

Understanding high load average with vmstat, mpstat, sar, and top

I am trying to understand the load average on my system when idle. Here are some results after the system has been running for a few hours, with almost nothing installed. vmstat root@arm:~# vmstat ...
0
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1answer
155 views

Slow USB 3 write speed

Writing to my USB 3 thumb drive (SanDisk Extreme SDCZ80-064G-FFP) is very slow on Linux: 1 GB takes longer than 200s. Using Windows (dual-boot on the same computer), the same 1 GB file can be copied ...
6
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1answer
2k 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 ...
1
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1answer
64 views

Apache Web Server Load Testing ( Running on Centos6) [closed]

How can i easily test how many requests my web server ( Apache) setup can handle without dropping a connection or timing out. Is there any simple bash script or i have to use some sophisticated ...
1
vote
2answers
44 views

Poor network performance between AIX 7.1 on 1 Gbit/s and SLES 11 on 10 Gbit/s [closed]

I am having problems with the network performance between SLES and AIX. I have tested the network performance from AIX 1 Gbit/s to AIX 1 Gbit/s SLES 11 10 Gbit/s to SLES 11 10 Gbit/s AIX 1 Gbit/s to ...
1
vote
1answer
16 views

Responsiveness of a CPU-busy RAM-moderate IO-moderate system [closed]

I am running computationally intensive multi-threaded jobs on my CentOS workstation with 4-core i5. Most of the time all 4 cores are busy, by memory usage is usually 25-50%, so there is no swapping, ...
1
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1answer
26 views

Install Linux to SSD or HDD for virtualizing Windows with QEMU?

In my PC I have 1 TB slow HDD and 120 GB fast SSD. I am curious which one of my drives should be used for Ubuntu installation. I plan to use Windows without dual-boot - by virtualizing it with QEMU (...
1
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0answers
23 views

Apache's sudden drop of requests

My server was working fine until a couple of weeks ago. All of a sudden, I started getting error notices from PHP. Lost connection to MySQL server at 'reading authorization packet', system error: ...
1
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0answers
25 views

HDDs, outer track vs inner track performance benchmarks?

I am interested in relating the position of a file on disk and the I/O R/W performance characteristics associated with this position. I have been able to find two benchmarks, but they are both for ...
0
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0answers
9 views

Unusual performance of libblas-dev on Unbuntu 14.04

The package libblas-dev in Ubuntu 14.04 seems to have unusual performance (much faster) in some cases in the following question. http://stackoverflow.com/questions/38042451/cblas-gemm-time-dependent-...
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3answers
59 views

Remove directories sequentially vs. simultaenously in background [duplicate]

Part of a script I am writing utilizes rm -rf to completely remove two directories. These directories are relatively large and can take a considerable amount of time to remove. Currently the ...
10
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2answers
4k views

echo vs <<<, or Useless Use of echo in Bash Award?

By now the Useless Use of cat Award is very well known, and there's also a mention of a Useless Use of echo (not relevant for this question). I'm wondering if there should be a "Useless Use of echo in ...
145
votes
1answer
322k 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? Note that this is mostly useful for benchmarking. Emptying ...
1
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1answer
128 views

Why kernel may be throttled?

My MBR start freezing up for over hour and I've found that my kernel reported being throttled, e.g. (this is just a sample for 2 seconds) $ sudo fs_usage | | grep -i throttled 12:26:45 THROTTLED ...
4
votes
1answer
3k views

Should I disable hyperthreading when concerned about performance of single-threaded applications?

I use a i5-2410M processor, which is setup to do hyperthreading by default on my laptop. Considering that this is a 2-core processor, this means it can do 4 threads at a time. This also means that ...
0
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1answer
40 views

HTML5 video performance

I have performance problem with video playing: When I am playing video on youtube, high CPU percentage is used: But when I download the same video and play it in VLC player, CPU usage is reduced ...
1
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0answers
37 views

Is the perfmon2 tool obsolete due to the same functionality being included in the current Linux kernel?

I was having some issues with the PAPI tool and multiplex and this answer by the PAPI creator led me to check out perfmon2: http://lists.eecs.utk.edu/pipermail/ptools-perfapi/2008-April/000900.html ...
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2answers
19 views

Proper way distribute several scientific experiments across multiple servers?

In case I have 8 powerful machines, what is the proper way to distribute and balance the load from user applications and scientific experiments? Is virtualization right way to go, or is there any ...
0
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0answers
16 views

server load and performance testing

Dears, there are some cluster of servers that are responsible for a telecommunication company databases. the OS's was Linux Redhat installed on bare metal till now, but all the clusters are migrating ...
2
votes
2answers
113 views

Tracking from httpd instance to PHP script when PHP is a module

I'm trying to figure out exactly what's going on that kicks CPU usage in random httpd workers so high but I'm having a little hard of a time figuring out what PHP page is being requested so that I can ...
2
votes
2answers
72 views

Slow scp transfer speed over wan

I have got a 300mbit symmetrical fiberoptic line, and I have got to transfer a 51MBYTE tar file from HOST A (fiberoptic 300mbit) to HOST B (digitalocean machine with more than gigabit bandwith). On ...
3
votes
0answers
229 views

router latency measured by tcpdump increases

I am using tcpdump to measure latency on a linux router, i.e. the delay experienced by packets as they pass through the router (made of Ubuntu 10). For this purpose, I captured packets in the IN and ...
1
vote
1answer
205 views

Reducing Number of MariaDB/MySQL Threads

So I'm running a MariaDB 10 database on a single core server; not super powerful, but then my needs aren't huge either. However, one thing I've noticed is that if I look in htop I have around 28 ...
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65 views

Debian 8 performance problems with good hardware

I bought about 6 months ago a good laptop (Lenovo ThinkPad E550 : Intel Core i5-5200U, 8 GO DDR3, AMD Radeon R7 M260) and installed Debian Jessie with Gnome 3 (no unity) on it. The system worked fine ...
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2answers
80 views

More efficient X-forwarding?

I open GUI remote programs by SSHing with the -X (or -Y) flag, e.g., $ ssh -Y user@host.com Recently, I found there is a much more efficient way to do this with web browsing only: $ ssh -DNNNN ...
1
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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 ...
1
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3answers
94 views

Is there any way of speeding up this DNS script I made? [closed]

Part of my work is doing a lot of different DNS lookups, so I created a script that displays the information that I need in a neat fashion. Problem is it's not very fast. Doing a bash -x I can see ...
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?
1
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1answer
39 views

How to obtain counters for swap-in/swap-out on Linux?

I'm trying to obtain counters for swap-in/swap-out activity on CentOS 6. The intention is to feed raw data into RRDtool to generate graphs, and use it to generate alerts. I've had a look at common ...
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0answers
35 views

Performance problem Fedora 23 32-bit @ Dell D630 4GB/Nvidia

I have installed Fedora 23 32-bit at Dell D630 4GB with NVidia Quattro NVS 135M (nvidia.ko, not nouveau.ko). And I have permanent performance problem as X-Windows (Gnome) are very slow and laggy. I ...
3
votes
1answer
70 views

What is the overhead of using subshells?

Hopefully this question is not too generic. I am very new to shell scripting and I come from a computer architecture/non-scripting programming background. I have noticed on the scripts at my work that ...
2
votes
1answer
47 views

'cd' complexity on ext4

In order to store attachments, a /path/to/atts/ directory will have numerous child-directories (product IDs) created (from 1 to ~10,000 or maybe more in the future), and in each of this subdir, 1 to ~...
26
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9answers
2k views

for vs find in Bash

When looping through files there are two ways: use a for-loop: for f in *; do echo "$f" done use find: find * -prune | while read f; do echo "$f" done Assuming these two loops will ...
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0answers
62 views

Why my server cannot serve more than 400 concurrent connections

I have an Ubuntu 14.04 LTS, kernel 3.13 in a Intel Xeon + 8Gb box. It has apache 2.4.7 configured in mpm worker with up to 4000 workers. The max bandwidth allowed by the ISP is 100Mbps. If I test ...
8
votes
1answer
3k views

Throttling web crawlers

My website is being DoS'ed by Google webspiders. Google is welcome to index my site, but sometimes it is querying a tagcloud on my site faster than my webserver can produce the results, making my ...
2
votes
1answer
49 views

How does iotop calculate the relative I/O activity?

I am running some heavy I/O processes on my workstation and recently installed iotop to monitor them. Here's a recent screenshot: I'm a bit confused about the readings in the IO> column. It ...
3
votes
0answers
31 views

Is it bad to have thousands of autofs rules?

My company literally has thousands of NFS volumes, which we need to mount on a few of our servers. However, we never mount all of them at the same time; typically we mount about 12 at a time. Most of ...
27
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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, ...
0
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0answers
13 views

Improving MPI performances on a heterogeneous cluster

I am running some parallel programs on a heterogeneous cluster: 2 CentOS virtual nodes (node 1 & node 2) on a Mac host and 2 others (node 3 & node 4) on a PC. When I run a parallel program (...
3
votes
1answer
23 views

Can I deny use of swap space to a specific process (and have it just get killed)?

While developing some software, a program under test sometimes eats all the memory, then proceeds to yomp into the swap space and start thrashing the disk, leading to a predictable drop in ...
1
vote
1answer
51 views

How to monitor system performance over time

I wrote the below script to determine how my system is holding up against various games. It checks all the vitals (GPU, RAM, and CPU) and then appends the data to a log file. Is this a reasonable ...