Questions tagged [performance]

The speed at which a program runs

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Rebinding many keys at once

My goal is to have a very accessible way to remap many different keys. More specifically I want the number row and the home row to swap positions on my keyboard when I press shift+space. Right now I ...
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How we can get performance metrics from VTune in command line of Linux?

I am going to record all performance metrics mentioned https://software.intel.com/en-us/vtune-amplifier-help-cpu-metrics-reference by using VTune in command line for my C++ code. I used $ amplxe-cl -...
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Why applications on FreeBSD run slower than on Linux?

Update They don't! At least, not for me. See my answer. Original question According to last year's Phoronix benchmarks, applications on FreeBSD mostly run slower than on Debian (including ...
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Can perf events detect deadlock in C++ codes (Linux)?

I am using perf tools to get some performance counters. I would like to know if it is possible to detect deadlock by checking performance counters included in perf events.
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Why is Arch GPU performance faster than Debian and Windows?

I have used Linux for a while, recently switching to Arch, and decided to test frame rates in Arch, Debian, and Windows. I first installed Windows (just drivers and Firefox, for I wanted to remove ...
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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 ...
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Want to capture host metrics for 60 min in every 3 sec through nmon

I want to run nmon for 60 min which will collect the host metrics in every 3sec. And to achieve this I run the below query on my host, nmon -ft -s 3 -c 60 /home/Documents/nmon When I analyze the ...
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1answer
31 views

How to speed-up programs launch with my ssd?

I have 2 disks on my machine: ssd and hdd. / mount point is on ssd, /home is on hdd. C:/ on my Windows 10 is on ssd, too. It seems to me that some programs (like Chromium web browser) launch much ...
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Alternative of too much slow gzip -d command

I'm using an production server for loading large data set to Hadoop to access from Hive table. We are loading subscribers web browsing data of Telecom Sector. We've large number of .csv.gz file (File ...
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97 views

System performance commands in Linux [closed]

How can I find determine real-time system performance parameters such as memory usage, CPU usage, disk usage from the terminal in Linux. I have asked Google but have not found a succinct suggestion. I ...
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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 ...
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Why does my system use more RAM after an hour of usage?

I am using Arch Linux (5.1.8-arch1-1-ARCH) with the XFCE DE and XFWM4 WM. Things are pretty elegant and low on RAM and CPU usage. After the boot, and when the DE is loaded completely, I see 665 MiB ...
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How to diagnose slow upload speeds on Ubuntu Server 18.04

I'm currently running Ubuntu Server 18.04 on a home server build to act as a Plex server, among other things. I have it connected via ethernet (with a 5-port switch between it and the router), and get ...
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What are the performance overheads between logging in to another user account via ssh vs login

In Gnu/linux systems, I can perform a full local login (i.e. where logname returns the same output as whoami) by two methods: login: sudo login second_user (prompted for password) ssh: ssh ...
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1answer
59 views

Why does rename() take longer when fsync() is called first?

In this test, why does rename() take longer when fsync() is called first? Environment: btrfs, mechanical HDD, Debian 9 container, running on kernel 5.0.17-200.fc29.x86_64. Test command: dpkg -r ...
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Slow wired connection on Linux but normal speed on Windows

I installed Ubuntu, Pop_OS, Manjaro, Neon, and Deepin, to my desktop PC (specs at bottom). My internet speed was very slow, basically unusable. Windows gives a normal 15 Mb down and 10 Mb up, but ...
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1answer
61 views

Could AIO fsync improve dpkg performance?

Could dpkg, the Debian package manager, gain a noticeable performance improvement by using one of the AIO fsync() operations, instead of sync_file_range() + fsync()? The [proposed] fsync2() API is ...
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1answer
76 views

How to limit frame-rate for all games on Linux?

System Linux Mint 19.1 Cinnamon 64-bit, based on Ubuntu 18.04 LTS. Related Hardware CPU: Intel Core i7-7700HQ (Ark Intel) GPU: NVIDIA GeForce GTX 1060 6GB (Max-Q Design) Screen: 4K laptop 15.6 inch ...
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1answer
28 views

Slow IO on OracleVM [closed]

We have a slow disk speed problem on the oracle vm's. Actually we have a same config two diffrent OVM(rac1, rac2), they works like active passive.they are oracle DB servers. One of them(rac1) no disk ...
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Huge hdd usage while gaming

For testing I tried to run Path of Exile and Guild Wars 2 on Ubuntu Budgie and Mint XFCE. To run PoE I used steam. To run GW2 I used Lutris. When any game is fully loaded and I do not touch anithing ...
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1answer
28 views

Does the “watch” command put stress on a scheduler?

I have an account on a compute cluster which uses the SLURM scheduler. I have some jobs in the queue and I'm using the "watch" command to see their status: watch squeue -u myUserName Does constantly ...
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1answer
124 views

transmission-daemon: UDP Failed to set receive / send buffer

I just compiled the transmission{-daemon,-cli} on my Debian 10 Buster, and installed it with some minor and major problems. One of those minor ones is apparent failure to set UDP receive buffer / ...
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1answer
80 views

Improve performance when using “system” call (shell escape) processing large files in awk

I have an awk script that processes very large files that look something like this: K1353 SF3987.7PD833391.4 KARE K1353 SF3987.2KD832231.4 MEAKE K1332 IF4987.7RP832231.2 LEAOS K1329 SF2787.7KD362619....
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2answers
108 views

NVMe disk shows 80% io utilization, partitions show 0% io utilization

I have a CentOS 7 server (kernel 3.10.0-957.12.1.el7.x86_64) with 2 NVMe disks with the following setup: # lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT nvme0n1 259:0 0 477G 0 ...
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In MPM “event” mode, when force killing an Apache2 process, what is the mechanism that creates a set of new Apache2 processes?

In MPM "event" mode, when force killing an Apache2 process, all other spawned Apache2 processes are killed. Within seconds, a batch of new spawned Apache2 processes are started by the main Apache2 ...
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1answer
74 views

IO wait time is higher than disk utilization. Isn't this impossible? [duplicate]

I am trying to improve my understanding, following this (so far) unanswered question: Possible limiting factor during upgrade of Fedora VM - not disk or cpu or network? I ran the following test load, ...
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1answer
38 views

Implications of using a plain string command instead of a function in .bashrc (particularly for PROMPT_COMMAND and PS1)

I have trouble understanding: How is .bashrc parsed How are bash functions constructed I try to customize my terminal prompt. My .bashrc make use of PROMPT_COMMAND like this (it's actually much more ...
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Possible limiting factor during upgrade of Fedora VM - not disk or cpu or network? [duplicate]

I'm upgrading a VM from Fedora 29 to Fedora 30. I triggered the update from inside GNOME Software. It downloaded the upgrade, and asked to reboot. It started installing... atop shows the qemu ...
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1answer
37 views

Finding performance bottlenecks on Red Hat server hosting KVMs with QEMU?

As a side task I administer a RHEL 7 server used as an internal KVM host. Now it runs eight VMs which, but for one, are idle most of their time, or at least not doing anything at all resource ...
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1answer
276 views

Huge performance difference of the command find with and without using %M option to show permissions

On my CentOS 7.6, I have created a folder (called many_files) with 3,000,000 files, by running: for i in {1..3000000}; do echo $i>$i; done; I am using the command find to write the information ...
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11answers
6k views

Why doesn't shell automatically fix “useless use of cat”? [closed]

Many people use oneliners and scripts containing code along the lines cat "$MYFILE" | command1 | command2 > "$OUTPUT" The first cat is often called "useless use of cat" because technically it ...
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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 ...
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1answer
161 views

LFTP - Remove files from remote server while uploading via lftp mirror --reverse

I'm using a shell script which executes lftp mirror --reverse to upload files and directories to a remote server. Just before that it removes everything using glob -a rm -r -f *. The problem is, it is ...
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2answers
116 views

How to search for large directory containing thousands of files?

Under the folder /grid/sdh/hadoop/yarn/local/usercache/hdfs/appcache we have more than 100 recursive folders. One of the folders contain thousands of files. Is it possible to identify this folder? ...
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1answer
90 views

Linux directories read/write behaviour?

I need to know how the directories of a Linux system are used, in relation to their approximate read/write behaviour in time. So far I have not been able to find any references. Can anybody provide ...
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0answers
47 views

Disk utilization on mdadm raid 5 is 100% even though none of the member disks is at 100%

I am currently confused about the disk utilisation of one of my machines. The setup: I have a machine containing 4 2TB HDDs. For those HDDs I used mdadm to configure a RAID 5 (called md2) On MD2, I ...
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1answer
39 views

Better more efficient bash script (grep)

I have a script that I built .. And it works fantastically -- BUT it's going to take an estimated 4 days to run! I was wondering if there's a more efficient way of doing this. Here's what the ...
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2answers
217 views

Why is `sed` no op much faster than `awk` in this case

I am trying to understand some performance issues related to sed and awk, and I did the following experiment, $ seq 100000 > test $ yes 'NR==100001{print}' | head -n 5000 > test.awk $ yes '...
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1answer
47 views

What is the fastest way to create multiple thousands of users on a system?

I need to create multiple thousands of users on a linux system. Currently I use the newusers command with a file as the source for all the users. The file contains around 10000 users. Running $ ...
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1answer
31 views

Performance reduction activating trace-functionality in kernel

Is there any performance reduction to be expected from just activating trace (ftrace) functionality in the Linux kernel, but not using it at run time?
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1answer
213 views

How does the Linux Kernel handle newer chips that patched only against Spectre Variant 1 but not Variant 2?

How will chips patched for Spectre Variant 1 and Meltdown, like Whiskey Lake and Amber Lake, handle Spectre Variant 2? I'm looking to spec out a new laptop. Currently evaluating the Lenovo x390. It's ...
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2answers
46 views

Bash Shell takes variable amount of time to load

I use bash on Ubuntu 18.04. I have added a lot of functions and a lot of scripts are sourced in my bashrc. I am able to time the total time it takes to load my terminal, sometimes it takes 0.9 seconds ...
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2answers
122 views

Debugging boot performance issues in grub / before kernel logging starts

My PC takes a long time booting. I have reason to believe it is caused by delays after grub, but before kernel logging starts (booting takes 30 seconds, but dmesg messages have time stamps between 0....
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1answer
125 views

filtering a large file with a larg filter

I want to extract all lines of $file1 that start with a string stored in $file2. $file1 is 4 GB large with about 20 million lines, $file2 has 2 million lines, is about 140 MB large and contains two ...
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How to diagnose the difference in OS performance between installation media?

I have two different USB sticks, a 128 GB Samsung and a 64 GB SanDisk. I used Gnome Disks to benchmark both of them and the Samsung one was supposedly better, it had faster read and write speed but it ...
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2answers
73 views

Long time spent between grub2 menu, before kernel boot

I installed a minimal ubuntu (xubuntu-core). It works well, but boot is a bit too slow. Right after I make my choice in grub, the screen turns black and after around 15 seconds I see the kernel boot ...
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1answer
366 views

efficiently grep an interval of a sorted file

My file has millions of lines, resides in memory /dev/shm/tmp.file, is accessed by multiple threads, looks like this 831092,25a1bd66f2eec71aa2f0a8bb3d,/path/to/a/file 4324,8d83c29e4d8c71bd66f1bd66fs,/...
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1answer
87 views

How to analyze top command results: CPU & RAM consumption

I am working on ARM-based processor (OS version: Linux 3.4.35) and I need to analyze the processor's performance while some processes are running, by typing top command, I can see some statistics but ...
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25 views

Sizing of Samba Linux Server

Do you know any performance of sizing recommendations about Samba 4.7.1 ? For few informations : 2vCPUs / 1 Core 8GB of RAM 140 simultaneous Windows users / 250 at most / 20 NFS volumes mounted via ...
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8answers
2k views

Is piping, shifting, or parameter expansion more efficient?

I'm trying to find the most efficient way to iterate through certain values that are a consistent number of values away from each other in a space separated list of words(I don't want to use an array)....