Questions tagged [performance]

The speed at which a program runs

189 questions with no upvoted or accepted answers
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6
votes
0answers
405 views

How to capture the xtrace output (only) in a file?

I know that I can redirect the xtrace output to some_file with something like this: exec 2 >> some_file set +x ...but this sends to some_file not only the xtrace output, but also any other ...
5
votes
0answers
338 views

Limiting per process dirty bytes without slowing down the whole system

Given a busy system with a really fast block device (highend NVMe raid, 2 GB/s write, 4 GB/s read) mounted at /data and an a really slow device (USB HDD with spinning 8 TB disk, 50 MB/s write, 60 MB/s ...
4
votes
1answer
146 views

Case insensitve tab completion zsh without increasing startup time significantly

So I wanted to get away from oh-my-zsh because it made my shell startup lag noticeably (>0.1s). Indeed, after removing oh-my-zsh the startup time went to 0.02s but now I started adding features ...
4
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0answers
496 views

Working out what is causing my machine to freeze

Background For a few years now, I have been having problems with my Xeon workstations freezing. For many things they have been lightning fast, but sometimes applications or even the desktop just ...
4
votes
0answers
330 views

How to mesure the latency of thread switching

I'm learning how to test the performance of a unix-like system. I've found a tool to measure the context switching time: http://www.bitmover.com/lmbench/lat_ctx.8.html Now I want to know if it is ...
4
votes
0answers
201 views

systemd slices even with low CPUShare heavily affect system responsiveness

I've created custom slice (so now I have 4 slices user, system, machine, important) and assigned huge number to CPUShares. System felt really unresponsive under high load in this slice, what seems to ...
4
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0answers
577 views

How to generate graphs from lmbench results?

I need to use the lmbench benchmarking tool to get the system performance statistics. I am able to execute and run the results. In the results folder this is a MakeFile with this information # ...
4
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0answers
106 views

Fixing terrible performance when watching/reading video and writing video files to disk

I have had this issue for quite some time and tried many times to fix it on my own and it always fails. IP schedulers, ionice and things like that always yield no result. I even went and bought an ...
4
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0answers
2k views

“Remote function call interrupts” (CAL in /proc interrupts). What is it?

I'm running a test program which generates a large number of threads and asynchronous I/O. I'm seeing very high counts of these interrupts in /proc/interrupts, the program cannot scale beyond a ...
4
votes
1answer
104 views

Timescales of any task in linux kernel?

I am studying how Linux kernel works and getting interested in the timescale of anything that happens in the kernel. Of course I know it depends on the HW, but would like to get an example. For ...
4
votes
1answer
611 views

GNU/Linux, IO performance problems

I have some problems with my system performance. As I was adviced here, I used sar: $sar -u 5 and found out that the problems are caused by a low HDD performance, as I supposed (high %iowait). My ...
3
votes
1answer
222 views

smb-share connection time increases each reboot on windows PE

We are currently developing a system that does automated BIOS updates for our computers. The system runs in Windows 10 PE booted via PXE-Boot. One of the first steps is connecting to a SMB-Share ...
3
votes
1answer
898 views

dd, ddrescue, dd_rescue performance according to OS (Ubuntu, macOS)

I put this question: recover files from HSF+ USB External HD, test on CentOS 7 to diagnostic And this https://askubuntu.com/questions/955325/using-gpart-testdisk-to-recover-gpt-for-files-from-...
3
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0answers
85 views

Why does bash appear faster on an Ubuntu VM than on the host MacOS?

This is the laptop sitting in front of me right now: On it is installed VMWare Fusion 8.5.3 with an Ubuntu 16.04 64 bit VM. I ran the following little test to compare performance between bash on the ...
3
votes
2answers
316 views

Verifying IO bottleneck

We are working on a project to benchmark systems in virtual machines that share the same physical host. I think we have a bottleneck with the system hosting the virtual machines, which may ...
3
votes
0answers
4k views

Increasing ulimit stack size benefits?

Hello I'm new in Linux and at my work I have a server that runs a banking software. The company that made the software said that the stack size should be set to unlimited. Does this make the software ...
3
votes
2answers
63 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 ...
3
votes
1answer
269 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 ...
3
votes
0answers
221 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. That said, I want to change that limit dynamically based on ...
3
votes
0answers
1k views

Send print job to printer immediately without queueing, aka increase print performance

I have a ruby/rails web application, one action of which sends PDF files that have been generated by the app to a Xerox 4127 printer on the network. This is accomplished via shelling out and running ...
3
votes
0answers
411 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 ...
2
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0answers
29 views

dd measurement question

I am wrestling with some perceived performance issues on a 3-node HPE Apollo cluster running Linux. (The cluster supports a backup application.) These are very $$ servers. In our setup each node ...
2
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0answers
42 views

What is the relation between IO wait utilisation and load average

Load average uses processes that are running or runnable or in uninterrupted sleep state. So do the processes in uninterrupted sleep state correspond with the %wa as per the top command? Both are ...
2
votes
0answers
40 views

Small delay in sudo

I want my zsh prompt to display whether the session has sudo rights (from a previously run sudo command). After looking at the answers to this question, I arranged to use the exit status of sudo -n ...
2
votes
0answers
85 views

Linux access windows share without loading to RAM

I have a laptop running an Arch-based Linux system and frequently need to access a windows share at my workplace. This is really annoying since it takes ages to load. Particularly, one folder is ...
2
votes
0answers
74 views

How important is os-variant for kvm configuration?

When searching the internet one can always read that specifying os-variant is important so KVM can optimize the guest system. Nowhere did I find an article, manual or documentation stating how ...
2
votes
3answers
117 views

Are there any practical reasons for setting a maxlogins limit for users in limits.conf? What are the benefits?

Why should I set a maxlogins limit in /etc/security/limits.conf? In other words, are there any performance-related and security-related benefits to be gained? I have only three users on my machine, ...
2
votes
0answers
2k views

How to find the cause of High Load Average on Linux

I trying to find the reason why my server is getting as high as 150 in load average, and some time it get up to 200. This is a Ubuntu Server running on a VMware ESXi virtual machine, with 8 CPU and ...
2
votes
0answers
75 views

Using a large number of nullfs mounts to create a virtual FS on FreeBSD - what are the practical limits + impacts?

I have a situation where I'm possibly going to create a virtual file system on FreeBSD, comprised entirely of nullfs mounts of selected "ordinary" dirs within my various ZFS datasets (and their ...
2
votes
0answers
316 views

what is the effect of setting cpu.cpu_quota_us in cpu cgroup?

I am trying to understand if setting cpu.cpu_quota_us in cpu cgroup subsytem has any impact on application performance. Essentially by reducing the CPU quota, but increasing the number of CPUs such ...
2
votes
0answers
824 views

Performance bottlenecks of Linux traffic shaping (tc)

I have an interesting problem. We have a Linux server with Debian Stretch installed. The server has a single CPU E5-2680 v2 and Intel 82599ES 10G Dual Port NIC's. There are no other services (like ...
2
votes
0answers
172 views

Performance of tar in a jfs2 with many small files

Observing the output of the tar command (-v flag) - observation by human eye - it seems to be pretty slower when it runs inside a sub-directory with about four hundred thousand small files (400000), ...
2
votes
0answers
137 views

How can I tell if my GPU is a bottleneck?

I already know of utilities like htop that can be used to (roughly) tell if a process is primarily bottlenecking at disk read/write speeds, network IO, not being parallel, or being parallel but ...
2
votes
0answers
95 views

Very low outgoing network speed

First of all, not sure at all if this is the correct place to ask. If it isn't, please forgive me. Well, I have an OrangePi zero as a server. I installed on it armbian (legacy, xenial version, kernel ...
2
votes
0answers
199 views

Is there a linux interface for arm cp15 register access?

For performance optizimization I should be able to switch bits in ACTLR register of the cp15 unit. I've done stuff like this before in bare metal projects, but from linux user space I can't execute ...
2
votes
1answer
484 views

Bad performance with Java

I have a computer that was running Windows with a lot of big programas (like Adobe Fireworks, and many other stuff) and the computer performance was really good. I decided to format my computer (I ...
2
votes
0answers
901 views

awk to process very large file

I have a file here where I want to tag each line with FILEB and FILEC as references. If column 1 of fileb or filec is in column 2 of filea, get the column 2 of fileb or filec (if column 1 file c ...
2
votes
0answers
537 views

BIND 9 intermittently slow

I'm running several Bind servers (v9.10.4) to provide DNS services to my users. Intermittently (about 30 seconds every 15 minutes) all recursive requests will fail and timeout. CPU and Memory on all ...
2
votes
1answer
748 views

Tuning sequential disk reads for performance

I am reading a large file sequentially from the disk and trying to understand the iostat output while the reading is taking place. Size of the file : 10 GB Read Buffer : 4 KB Read ahead (/sys/block/...
2
votes
0answers
42 views

Investigating annoying short UI hangs

I just bought a new desktop machine for home (see system details below). It's supposed to be super smooth, but nevertheless I'm experiencing quite frequent UI 'stutters'. It's as in the olden days ...
2
votes
3answers
327 views

Display “burps” every 30 seconds

I'm running Mint 18 on a Dell i7 and I have this annoying issue that I can't find where its coming from. Every 30 seconds the display freezes for about 0.5 seconds. The issue is persistent and ...
2
votes
0answers
185 views

Benchmarking under SELinux Sandbox with Phoronix Test Suite

I would like to run the Phoronix Test Suite 6.2.2 under the SELinux sandbox on Fedora 23, but I can't execute it using $ sandbox ./phoronix-test-suite. I probably don't have the correct SELinux type. ...
2
votes
0answers
1k views

ZFS (on linux) performance issues

I have a server setup with RaidZ2 (8 disks in array) + 2 spares (+ system disk). The disks are 6TB each, 7200 RPM SAS The machine runs Centos7 x86_64 (not a VM), and has 128 GB of RAM and 48 cores (...
2
votes
1answer
5k views

RHEL 7 Still CPU Frequency Scaling

When machine is imaged with: RHEL6.x CPU speeds report full 3.3Ghz speed for all CPUs cpupowerutils is not installed RHEL7.x CPU speeds vary (shown in example below) cpupowerutils is installed I ...
2
votes
0answers
829 views

Debugging Slow Queries in MariaDB/MySQL

I've set up a MariaDB server and everything is running well, with most queries executing in well under 20 milliseconds, but every so often a query will take half a second or longer (sometimes several ...
2
votes
1answer
263 views

Is “top” accounting for Kernel Interrupts?

I have a simple interrupt that is triggered by a GPIO-input. The IRQ only increments a variable and returns. When I turn the frequency of the interrupts up to somewhere around 10-20 kHz, the system ...
2
votes
0answers
789 views

How does performance measurement tool 'perf' actually work?

perf is a tool which accesses the performance counter registers of an machine and gives out metrics to user to analyze the system performance. What I am curious about is, when I read the parts of ...
2
votes
0answers
1k views

Linux Mint 17.1 Cinnamon is slower in computer than in Virtual Box

After some months working in a VirtualBox VM with Linux Mint (the host as a Windows 7), I've finally installed Mint 17.1 Cinnamon on the same computer. And the experience hasn't been good. The fact ...
2
votes
0answers
402 views

How to use blktrace to monitor the eMMC Flash access pattern?

I'm trying to simulate a FTL(Flash Translation Layer) algorithm and evaluate its performance. What I need is a trace file of a flash access(containing information about block and page access). I'm ...
2
votes
0answers
136 views

JVM low-memory tuning

What command-line options would provide the lowest memory-footprint JVM, in OpenJDK, or possibly other JVMs (Linux/Debian)? I'm willing to disable JIT, live with slow or choppy garbage collection, ...