0
votes
1answer
47 views

Slow Linux machine [on hold]

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 ...
2
votes
0answers
30 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
23 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 ...
0
votes
1answer
49 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 ...
0
votes
0answers
28 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
45 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 ...
1
vote
1answer
67 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 ...
5
votes
1answer
126 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 ...
37
votes
1answer
2k views

Diagram of Linux kernel vs. performance tools?

Is there a diagram that shows how the various performance tools such as ip, netstat, perf, top, ps, etc. interact with the various subsystems within the Linux kernel?
6
votes
7answers
555 views

Make disk/disk copy slower

Is there a method of slowing down the copy process on Linux? I have a big file, say 10GB, and I'd like to copy it to another directory, but I don't want to copy it with full speed. Let's say I'd like ...
3
votes
3answers
406 views

Can I just disable updatedb?

Is updatedb necessary at all? I never use locate and my servers tend to have dozens of millions of files which usually makes updatedb to run for a long time and consume I/O needed by MySQL and/or ...
1
vote
0answers
15 views

Amount of memory transfer on a running Linux

Can I determinate the amount of RAM exchange (between the CPU and the RAM) on a running Linux system? I'm not looking for the max RAM speed (then memtest would be valid answer). I'm looking for the ...
4
votes
2answers
685 views

Why is dd using direct slower writing to disk than to a file

I am trying to compare aggregate write rates when writing to a file in a GPFS file system, as compared to writing directly to a disk on a system with Red Hat Enterprise Linux Server release 6.4 ...
0
votes
2answers
41 views

Fedora 17 Performance Issues [closed]

I have a Dell Latitude E4310. I have Windows 7 and Fedora installed on it. I rarely use windows and I have been using fedora for a good 9 months now. Recently the performance on my machine degraded ...
1
vote
1answer
1k views

Running thousands of curl background processes in parallel in bash script

I am running thounsand of curl background processes in parallel in the following bash script START=$(date +%s) for i in {1..100000} do curl -s "http://some_url_here/"$i > $i.txt& ...
3
votes
4answers
208 views

Does cron jobs per se represent a significant burden on a modern system?

I'd like to run a pretty simple script (is there a dir with name x in dir y if so move it to dir z–and x will only be there about once a day) every 15 seconds or so (one minute divided into 4*15 ...
2
votes
1answer
42 views

Multiple Lan interfaces on one VM rather than multiple VM

I'm looking if it's possible to give rights, to only allow the use of one network interface to a specific user on a Linux distribution. My use case: I want, for my studies, testing the ...
3
votes
2answers
406 views

Massive, unpredictable I/O performance drop in Linux

I'm using Debian testing without any problems for ~6 years (I'm just regularly updating it), but recently it started to show a random behaviour that can be summarized as "Low I/O performance which ...
12
votes
1answer
5k 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?
3
votes
1answer
186 views

How accurate is Conky?

I'm on Crunchbang 64 bit, Conky shows that I'm using 4% of my CPU. But I can feel the CPU burning so hot, got Spotify, Chrome and couple other apps running. On windows 7 chrome uses about half of the ...
3
votes
1answer
291 views

Linux: How to check whether a process is slowed down by other running processes

I have one process running on a RHEL 6.3 machine. Somehow this is taking a longer processing time than the same process running on another machine. How is it possible to know why this process is ...
0
votes
1answer
459 views

What does high, low, negative and constant values from pidstat command mean?

I needed information on the following: Can you please tell me the inference for the following in terms of high, low, negative and constant values from pidstat command in Linux. kB_rd/s, kB_wr/s, ...
0
votes
1answer
95 views

Is my approach to performance testing in Linux environment correct?

I want to do performance testing in a Linux environment for a C++ application. I need to measure the CPU & Memory usage of the application. This application is a multi-threaded application. In ...
0
votes
1answer
1k views

ulimit & rlimit in Linux, are they the same thing?

I see people use the terms ulimit & rlimit interchangeably, can I say they are referring to the same thing?
4
votes
2answers
688 views

Inotifywait for large number of files in a directory

What I want to do is, to monitor a directory (not recursive, just one) for new files created and append those files to one single big file as they are being written. The number of files that are ...
1
vote
1answer
420 views

Measurement of free ram through /proc/meminfo with ramdisk (initrd)

I am booting a disk image via PXE, it is a full system on an initrd ramdisk. I would like to measure the actual free memory of the system (not including buffers and file system caching). I was told ...
3
votes
1answer
533 views

How does irqbalance determine which package to use?

irqbalance --debug shows the following: Package 0: Core 0, 2, 4, 6, 8, 10, 12, 14 Package 1: Core 1, 3, 5, 7, 9, 11, 13 When I run network applications, it seems like IRQs are being handled by ...
6
votes
1answer
400 views

Determining LVM Extent numbers for given file

I'm currently engaged in a non-work related homework exercise. I have an ext4 filesystem sitting on a logical volume. I'm testing different performance tuning strategies and this idea occurred to me. ...
1
vote
1answer
113 views

Establishing I/O Patterns for an Application

Are there any system tools that allow you to profile an application's usage of storage? Basically, I'm looking for information on determining whether there are more large sequential reads, tiny ...
1
vote
1answer
385 views

vmstat on virtual machine and large values

Hi I'm using vmstat to track machine performance during some tests (jmeter). This is virtual machine running on a big machine where lots of other virtual machines are installed (about 20 virtual ...
1
vote
1answer
108 views

How to configure Linux to run benchmarks as stable as possible?

I have several long running benchmarks (SPEC CPU 2006 benchmarks) to run on a Linux server. The server is running Gentoo Linux with a Linux Kernel 3.6.11. I saw some big differences between ...
1
vote
2answers
506 views

btrfs performance

I decided to mess around with btrfs and found some weird performance anomalies. The tests I've done are with with two external hard drives one formatted with ext4 the other btrfs. ext4 performance ...
2
votes
0answers
279 views

Local disc copy at 10MB/s! What could be the problem?

I am running a Debian 6.0.6 (before you ask). I have a regular desktop computer, nothing fancy... but when I copy a file using nautilus I am getting 10MB/s copy speed and the system is completely ...
5
votes
2answers
733 views

Linux (3.4) SSD swap partition usage causes extreme latency - how to eliminate?

I'm running on 4G RAM with an extra 6G swap partition, SSD is a pretty decent SAMSUNG MZMPA128HMFU model. System responds very well to workloads when things stay in RAM, but as soon as things reach ...
3
votes
1answer
931 views

Linux disk I/O performance issue — what config options to look at?

We discovered an I/O related performance problem when using the default SLES11 SP2 kernel. Our same application on the same hardware had no issue with (the admittedly ancient SLES9 SP3). We had a ...
0
votes
2answers
197 views

Is it against linux ethos to provide a progress indicator for running commands? [duplicate]

Possible Duplicate: Why doesn't cp have a progress bar like wget? Lately I have been dealing with rather large files in Linux. I often use commands like sed, cut, sort, uniq, awk, and ...
2
votes
1answer
272 views

Book or online article on analysis and tuning Linux system performance [closed]

I am looking for a good book or online article on analysis and tuning Linux system performance. So far I've found openSUSE 12.2 System Analysis and Tuning Guide which looks promising. Any other ...
4
votes
1answer
189 views

Linux mutex spins [closed]

On Solaris I can use mpstat to see the smtx (i.e., spins on mutex or in other words locks not acquired on the first try) value. This value increasing indicates that swap is being hit too frequently ...
4
votes
2answers
1k views

Linux running slow with 0 swap left

Our Linux server is responding very slowly. top doesn't show any excessive CPU usage. I noticed that even though there's about 5GB of free memory, the system is using all of swap with no free swap ...
5
votes
4answers
1k views

How to get better desktop performance in linux?

Normally I do not care much about desktop - performance, since my servers do not run any gui. But at home I run some older hardware (Pentium) which gets sometimes very sluggish (mouse-movements in ...
4
votes
2answers
872 views

Is it possible to trigger OOM-killer on forced swapping?

Is it possible to have the system preemptively swap out inactive pages (vm.swappiness), but invoke the oom-killer when the system runs out of RAM (as opposed to running out of memory) and is forced to ...
1
vote
0answers
214 views

Connected external HDD slows down system

I need to connect large external hard disks (with many many files) to a system running Ubuntu. I have no idea how the Linux kernel is treating the inodes for the external drives, but attaching huge ...
2
votes
1answer
253 views

How do I record disk performance on slow hardware and then replay it to faster hardware and benchmark it?

I am currently performing various development tasks that are slow on my current system because of IO performance. Is there a way to record disk operations while performing IO consuming tasks, ...
2
votes
0answers
287 views

Software raid checksumming slow

On my new 24 disk array I get 900 MB/s of raw read or write using dd to all the disks. When I set the disks up as a 24 disk RAID6 I get 400 MB/s write and 600 MB/s read. It seems to be due to ...
2
votes
2answers
1k views

vmstat IO stats: why the high bo during a download?

On my RHEL 4 machine, I was downloading a huge file (2.5GB)..I was checking the output of vmstat and was especially curious about seeing the disk IO using bi and bo. I know iostat is a better tool ...
40
votes
5answers
20k views

Can I configure my Linux system for more aggressive file system caching?

I am neither concerned about RAM usage (as I've got enough) nor about losing data in case of an accidental shut-down (as my power is backed, the system is reliable and the data are not critical). But ...
5
votes
1answer
816 views

SysBench highlighting abysmal disk write performance on white box vs Tier1 server

Have been testing white box system with SuperMicro X8DTL motherboard with various SATA hard disks such as 7,200RPM Seagate Constellation ES and 10,000 RPM Western Digital VelociRaptor. Have tested ...
5
votes
2answers
4k views

is there an open source tool to measure cpu performance?

I have used many times ab for measuring web performance, hdparm for measuring hard disk performance and netperf for measuring network performance. But I didn't find any tools to measure cpu ...
16
votes
3answers
13k views

What is the most high-performance Linux filesystem for storing a lot of small files (HDD, not SSD)?

I have a directory tree that contains many small files, and a small number of larger files. The average size of a file is about 1 kilobyte. There are 210158 files and directories in the tree (this ...
2
votes
1answer
1k views

Interpreting tiobench results

I'm running tiobench on my raid1 and it gives me the following results. Why is there ##### shown instead of throughput? Why does seq.reading with 8 threads use 2836% CPU? My results: $tiobench No ...