Questions tagged [optimization]

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Is it safe to disable clamscan and clamd services on linux server

We have a dedicated CentOS server with 8 CPUs. We often observe clamscan and clamav taking too much CPU. I have heard experts saying linux doesn't require an antivirus. If that is true, is it safe to ...
1
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1answer
33 views

Speed up random sort and delete (rm) for multiple directories

Running MacOS in a terminal which is essentially BSD, hence posting my question here instead of askdifferent. I want to trim my image dataset down in subsequent steps, by deleting files randomly. Some ...
4
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0answers
127 views

Compile a library aiming to reduce size as much as possible

I have to 'squeeze' all the needed code to run ldaps on an embedded system. So the 3 MiB of lybcrypto and almost 700KiB of libssl are way too much. I'm now experimenting on ldapsearch because reading ...
2
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0answers
48 views

Nested Virtualization [closed]

I want to deploy openstack with nested virtualization enabled. Here is the scenario, on physical machine (Ubuntu 16.04) I have 2 VMs running, 1. kvm01 and, 2. cmp001 Kvm01: has 7 VMs up and running ...
2
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1answer
875 views

Why can the kernel not use SSE/AVX registers and instructions?

This post from StackOverflow has this, In some environments there there is a restriction on certain instructions or using certain registers. For example, in the Linux kernel, use of SSE/AVX or FP ...
1
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1answer
107 views

Fastest way to count zero bytes on a partition

My root and home partitions are LUKS-encrypted. I wish to have discard/TRIM enabled on them (I'm aware of security implications). If my understanding is correct, this should result in discarded areas ...
-1
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1answer
905 views

Why configure/build gcc takes much more time than apt-get install gcc [closed]

Wander to make some modification on libgomp (gcc's OpenMP runtime library), I downloaded the source code of GCC8, and tried to configure/make the whole compiler. The configuration phase terminated ...
6
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3answers
831 views

Do file descriptors optimise writing to files?

Is it equivalent to have commands print to a file directly, as opposed to writing to a file descriptor? Illustration Writing to file directly: for i in {1..1000}; do >>x echo "$i"; done ...
1
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1answer
302 views

Set usb flash drive as non rotational drive

I'm trying to optimize the IO schedulers and to use a proper scheduler for rotational and for non rotational drives (different). When I run: cat /sys/block/sd*/queue/rotational I get: 1 <-- ...
4
votes
3answers
82 views

Script optimisation to find duplicates filename in huge CSV

I have several CSV file from 1MB to 6GB generated by inotify script with a list of events formatted as is: timestamp;fullpath;event;size. Those files are formatted like this : timestamp;fullpath;...
3
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2answers
1k views

How to force a Thinkpad to draw charge from internal vs external battery?

My T450s Thinkpad has two built-in batteries--one hot-swappable and one inside the laptop. Lenovo calls the former "external" and the latter "internal". When not plugged in, the external battery ...
1
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2answers
203 views

Does zgrep reuse recently uncompressed files?

I am calling zgrep over *.gz files in a for loop in one directory. As the log files are huge (about 1GB each, and about 30 files), the command is taking a long time. I see several uncompressed files ...
1
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1answer
153 views

How do you specify a blkparse format specifier that also suppresses summary

When using the live mode, I do: blktrace -d /dev/sdc1 -o -|blkparse -f '%a %c' -i - I just want to limit the displayed data to 'action' and 'cpu id'. Instead I get the summary and all the usual ...
6
votes
1answer
320 views

How to create a configuration to only connect to WiFi if signal is ≥ 30 %?

Is there any chance to create a configuration that does the following job? Only connect to available WiFi if it's signal is stronger than 30 % At many places, I stay in the border area of barely ...
3
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0answers
178 views

How do backreferences slow down regular expression search?

Let's say I have a text file with 20 chars per line like this: wertzuiopasdfghjkl< asdfghjkl<yxcvbnm,.- <yxcvbnm,.-123456789 1234567890QWERTZUIOP QWERTZUIOPASDFGHJKL< and so on ... and ...
1
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0answers
61 views

Optimal value for make -j <value> [duplicate]

What is the optimal value of the -j flag for make ? I know that all my source is free of errors. Is it the number of cores? Or the number of logical processors?
1
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1answer
183 views

How to increase no. of nfsd threads in WD my cloud (nfs server)? for better performance

There are only 8 default nfsd threads available in WD my cloud, this no. is not sufficient for my requirement. I want to increase default nfsd threads to 20 threads. For this I first connected with ...
2
votes
0answers
195 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
0answers
119 views

selinux user add becoming progressively slower

I've written a service that configures a machine with selinux users who can manage a single port. I'm trying to pre-seed that machine with 1000 users, but selinux is crawling to a halt around user ...
12
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1answer
524 views

How does ksh93 avoid forks in command substitution

Given cmd='fun(){ echo "$@"; }; fun $(fun $(fun hi))' shells tend to need to make 2 forks to make it happen strace-f(){ strace -f "$@" 2>&1; }; for sh in dash bash zsh ksh; do printf ...
16
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5answers
10k views

Compress a large number of large files fast

I have about 200 GB of log data generated daily, distributed among about 150 different log files. I have a script that moves the files to a temporary location and does a tar-bz2 on the temporary ...
6
votes
1answer
1k views

SSD optimization

I know this has been discussed many times, but there are a lot of different opinions across the internet which optimizations are good for SSDs (and whether to use them). Also the technology has ...
1
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2answers
786 views

Optimize/Replace 'find' command

I am looking to optimize this find command. We have to move a bunch (sometimes almost a million) files to a directory for further processing. We are looking for a way to increase the speed of this ...
4
votes
2answers
187 views

How do I write a script to automatically optimize all the PNGs in my MediaWiki images directory?

I have MediaWiki 1.25.2 installed on my 64-bit Debian 8.1 VirtualBox machine and I'd like to be able to upload the images/ directory from this installation to my DropBox. Being a cheapskate I'm trying ...
1
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0answers
62 views

VNC rendering is all fragmented

I have my VNC server so configured, that it requires me to establish an ssh tunnel and connect to it on localhost:1 with my vncviewer. Now the connectivity seems to work fine but the rendering of the ...
5
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4answers
19k views

How to calculate the memory consumed by a “C” program in linux

I have written two C programmes one is using function pointer, and the other without function pointer. Now i want to know the memory consumed by the two programmes , to see how memory can ...
1
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0answers
218 views

What are the consequences of disabling nmi_watchdog?

My aim was to improve battery life for my laptop. I have already applied some advised modifications like enabling ALPM, and adding pcie_aspm=force drm.vblankoffdelay=1 i915.semaphores=1 at grub ...
2
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0answers
346 views

Ubuntu Bootchart - How do I actually interpret this chart?

I'd like to start obsessing over optimizing my Ubuntu boot time, but I've searched online for multiple days—and only have a vaguely more coherent idea of what I'm looking at. Here's my bootchart. I ...
15
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3answers
27k views

How to compile without optimizations -O0 using CMake

I am using Scientific Linux (SL). I am trying to compile a project that uses a bunch of C++ (.cpp) files. In the directory user/project/Build, I enter make to compile and link all the .cpp files. I ...
1
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1answer
739 views

How to speed up an apache webserver?

We have a PC: Intel(R) Core(TM)2 Duo CPU E7300 @ 2.66GHz 3 GByte RAM HDD: 160 GByte WD1600AAJS-08L7A0 And we have Ubuntu 12.04 on it with apache 2.2.22-1ubuntu1.7. Serving just static HTML files (...
4
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2answers
340 views

CPU optimized compiled debian packages

I really don't know how the Debian maintainers check for all the bugs in every release of Debian, but isn't it the case that if all codes for every package have been patched up and tested for all CPU ...
2
votes
1answer
72 views

optimisation of bash globs

Looking for a guide to optimising regexp matches in bash. I have a script that loops over a very long list of URLs looking for patterns. Currently it looks a little like the fragment below. Is there ...