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Questions tagged [performance]

The speed at which a program runs

7
votes
2answers
3k views

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 ...
1
vote
0answers
44 views

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 ...
0
votes
0answers
21 views

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 ...
0
votes
1answer
48 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 ...
1
vote
0answers
27 views

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 ...
1
vote
1answer
52 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 ...
1
vote
1answer
50 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 ...
0
votes
1answer
24 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 ...
0
votes
0answers
17 views

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 ...
0
votes
1answer
27 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 ...
0
votes
1answer
80 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 / ...
1
vote
1answer
71 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....
2
votes
2answers
97 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 ...
0
votes
0answers
7 views

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 ...
1
vote
1answer
54 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, ...
1
vote
1answer
37 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 ...
1
vote
0answers
24 views

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 ...
2
votes
1answer
35 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 ...
6
votes
1answer
266 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 ...
27
votes
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 ...
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 ...
-1
votes
1answer
78 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 ...
1
vote
2answers
95 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? ...
0
votes
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 ...
1
vote
0answers
45 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 ...
1
vote
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 ...
5
votes
2answers
203 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 '...
2
votes
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 $ ...
0
votes
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?
5
votes
1answer
185 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 ...
0
votes
2answers
45 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 ...
0
votes
2answers
92 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....
2
votes
1answer
116 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 ...
0
votes
0answers
17 views

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 ...
1
vote
2answers
70 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 ...
5
votes
1answer
335 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,/...
1
vote
1answer
77 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 ...
0
votes
0answers
23 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 ...
24
votes
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)....
0
votes
0answers
9 views

The nginx provide data download rate is not meet the iperf3 test

I use iperf3 test the IP, there gets 9.3G/s [root@localhost ~]# iperf3 -c 4.4.226.59 Connecting to host 43.224.226.59, port 5201 [ 4] local 4.4.226.69 port 57212 connected to 4.4.226.59 port 5201 [ ...
0
votes
2answers
98 views

Fast hashing in awk?

I find it cool that someone has written MD5 in AWK: https://kaworu.ch/blog/2017/05/23/implementing-md5-in-AWK/ Unfortunately that one is quite slow. I am looking for a fast hashing tool for AWK that ...
4
votes
1answer
111 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 ...
3
votes
2answers
141 views

Linux GUI becomes very unresponsive when doing heavy disk I/O - what to tune?

I have a device /dev/mydisk that is based on a stack of functionality: a LUKS-encrypted, software RAID-1. From time to time, I do a backup of /dev/mydisk contents to an external USB disk, which is ...
0
votes
0answers
55 views

Samba shared folder over openvpn very slow - Linux OS

Recently I've installed Ubuntu 18.04 and I've noticed that sharing a samba folder from a Linux server over a openvpn tunnel is very very slow. Tried to avoid using DNS, but still have no results. ...
0
votes
2answers
40 views

How to remove trailing CR quickly?

This is my source file, it dumps a database into a JSON and worked great with Debian wheezy: #!/bin/sh echo "Status: 200" echo echo { printf ".mode csv\nselect * from cfg;" | sqlite3 /home/ftproot/...
1
vote
2answers
44 views

Speeding up repeated python calls (or, alternatively, porting a complex regex to sed)

I am an academic medical physicist. I do experiments that generate a fair amount of data, and they are expensive to run. My university has a backup system that consists of a robot tape library in a ...
2
votes
1answer
39 views

Improving performance of Script Using find and exec [closed]

I have a script that iterates through a given directory and automatically compresses those that do not contain at least one file used in less than 30 days. Now, I am wondering if I could improve ...
0
votes
1answer
25 views

OS keeps getting slower the more time I leave it open

I recently decided against shutting down my Ubuntu machine in office because it took a lot of time to start it and then open all the applications that I would normally require. After leaving the PC ...
0
votes
1answer
24 views

mv command for many nonexistent files, does it wear off the destination disk at all?

I am trying to continuously move many files (~ 10 000 each minute) from /ramdisk to normal /ssd , but not all files are there. When the mv /ramdisk/file55 /ssd/file55 fails because source is not ...
3
votes
1answer
99 views

Why would NFS have lag after a minute of inactivity?

I am running a version 4 NFS server on a Salix server with kernel 3.10.17. I am mounting the NFS share with the command sudo mount -t nfs 10.0.0.150:/share /mountpoint on my client machine, which is ...