The speed at which a program runs
3
votes
2answers
53 views
Why is writing to a existing file faster than write a new empty file?
I use MappedByteBuffer to write file in linux.
File file = new File("testFile");
RandomAccessFile raf = new RandomAccessFile(file, "rw");
FileChannel fc = raf.getChannel();
MappedByteBuffer mbf = fc....
1
vote
0answers
27 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 ...
1
vote
0answers
59 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 ...
0
votes
0answers
9 views
Is there a simple key-val storage system built in? [duplicate]
I've started preferring key-val storage over SQL. I'm hoping there's something built in that's a littler than pstore or redis.
I've been doing a lot of string (de)serializing of lists and ...
0
votes
1answer
28 views
Linux: CPU load sharing on new server
We have got a new Linux el6.x86_64 server and after moving all our jobs (primarily java/C++/python/shell) processes onto this new server, we have observed the processes running slow.
E.g. A python ...
0
votes
1answer
61 views
Very bad wireless performance
I'm struggling with very poor wireless performance on a Fedora 25 setup running kernel 4.8.15-300.fc25.x86_64.
When downloading anything via wget, I get like 5Kb/s, and downloads usually stop. If I ...
1
vote
3answers
48 views
Does keeping empty space in /home/$username has any benefit?
I have 3 partitions -
/ - This has something close to 200 GB (more than anything else I might need in near or far future)
swap - 2 GB
/home - 200 GB
/data - 500 GB (all those movies)
Now unlike ...
0
votes
0answers
18 views
KVM RAM Performance
What is difference in performance between RAM in native system and virtualized RAM in KVM for guest OS?
I know that I can set hugepages, but I do not want, because if I set, I will lost some RAM at ...
1
vote
1answer
59 views
Faster startup of zsh [closed]
I love tmux, but whenever I need to create a split with a new pane or a new window it has to run my zsh init scrips and .profile, etc. And they take about a few seconds to run. Initializing stuff like ...
0
votes
0answers
14 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 ...
0
votes
1answer
8 views
PostgreSQL: Speed over reliability config
For my development machine I need no data consistency in case of a crash. Is there a config for a Debian-like system, that optimizes PostgreSQL for speed (even if it sacrifices reliability)?
So ...
1
vote
0answers
45 views
Fedora behaves sluggish after the upgrade 24 → 25
I have upgraded my Fedora installation from 24 to 25. Since then, things that were done instantly before sometimes take half a second now. Examples are:
Switching the workspace in Awesome WM
Typing ...
1
vote
1answer
44 views
Why is dig query time slower on one computer vs another in the same LAN?
To make a long story short, I setup DNS forwarding/caching using dnsmasq built into my router (EdgeRouter).
My test command is simple:
dig www.example.com
On one computer, which happens to be a ...
3
votes
1answer
110 views
What are Kernel PMU event-s in perf_events list?
Searching for what one can monitor with perf_events on Linux, I cannot find what Kernel PMU event are?
Namely, with perf version 3.13.11-ckt39 the perf list shows events like:
branch-instructions OR ...
11
votes
1answer
173 views
How to ensure exclusive CPU availability for a running process?
At first, the question seems to be a little bit silly/confusing as the OS does the job of managing process execution.
However, I want to measure how much some processes are CPU/IO-bound and I feel ...
2
votes
2answers
154 views
Local unix socket - rough idea of throughput
Is anyone aware of throughput benchmarks / measurements for using a local unix socket for inter-process communication?
I want to illustrate the performance benefit of having a local database ...
1
vote
2answers
106 views
Bash script performance
In a bash script, some integers in a range are generated, concatenated with fixed strings, and printed on a file. OS is Ubuntu 14.04 and bash version is 4.3.11(1)-release.
The strings (and so the ...
9
votes
2answers
392 views
VirtualBox: Is it a bad idea to assign more virtual CPU cores than number of physical CPU cores
As I have a Hyper-Threading capable CPU, I wonder, is it a bad idea to assign more virtual CPU cores than number of physical CPU cores as the following warning suggests:
Transcript:
More virtual ...
1
vote
1answer
50 views
What are the consequences of having many files in a directory in an ext4 filesystem?
My task is to store a list of JSONs on disk (without using any database) and I have these options:
Store them in a single, large file.
Store them in separate files, keyed by their IDs.
Personally I ...
3
votes
0answers
15 views
Larger number of context switches for kondemand
According to the documents on the web, kondemand is responsible as cpu scaling governor.
kondemand is a kernel thread that belongs to the ondemand governor of cpufreq subsystem, which changes the ...
1
vote
1answer
41 views
finding the root of high CPU load
The output of top command shows that CPU load is about 82!. The system has 32 cores. Normally, each core increment the load by one.
How can I find out what is exactly happening?
top - 11:20:43 up 88 ...
1
vote
1answer
62 views
Change order of startup services with systemd
Currently, my computer starts up a lot of services (like docker, apache2, mysql, networking) before showing the log in screen. I want to start these services after the log in screen, so that booting ...
1
vote
1answer
70 views
How to use AWK to query a file loaded with mapfile [closed]
I am using awk on Ubuntu to corelate references between two log files (In.log and Out.log).
It is working as expected, but went the size of the Out.log increase (~K lines), the processing time ...
1
vote
0answers
15 views
multiple directories for sar command
Is it normal for below directories created by sar command
-rw-r--r-- 1 root root 348948 Nov 3 23:50 sa03
-rw-r--r-- 1 root root 348757 Nov 3 23:53 sar03
-rw-r--r-- 1 root root 348948 Nov 4 23:50 ...
0
votes
0answers
60 views
vlc can't play H264 smoothly while mplayer can
I have video playback issues with vlc while mplayer performs correctly.
Sample file
Caminandes 1: Llama Drama
Type : Vidéo
Codec : H264 - MPEG-4 AVC (part 10) (avc1)
Resolution: 1920x1090
...
3
votes
1answer
67 views
Does dm-crypt utilize multiple cores? (Interested in multi-core Pi clones)
I'm considering replacing single-core Raspberry Pi with an encrypted disk with multi-core Banana Pi M3. Encryption/decryption performance is currently the bottleneck, so I'd like to know if encryption ...
1
vote
4answers
105 views
Is there any linux command to speed up the execution of the files?
I would like to know if there is any linux command to execute the perl file faster?
I used the following command to check execution time:
time ./rspd.pl
output:
1.003u 0.480s 3:34.90 0.6% 0+0k 56+...
3
votes
1answer
56 views
Which command produces more data per second?
Which command produces more data per second? This could be useful to quickly fill a file with garbage data or to test data transfer rates. So far, I found that "/dev/zero" is the quickest one.
$ cat /...
0
votes
0answers
90 views
Performance problems with Intel Graphics under (but not limited to) Linux Mint 18
So, since I've nuked my storage and reinstalled everything from scratch, I've been having issues with graphical performance.
My PC specs:
Dell Inspiron 5437-A20
Intel Core i7-4500U
8GB DDR3 RAM
...
0
votes
1answer
45 views
Phantom CPU usage
I have a bunch of VM's which all are practically the same. All are set up as a clone of 1 reference machine. On only one of them xentop gives me a continues load (idle?) of around 102%. After looking ...
3
votes
1answer
49 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
1answer
130 views
Java equivalent of strace
When I have an issue with a C application, one of the first tools I reach for is strace, I can easily see e.g. if it is blocking on a read from a socket, or for some file I/O or whatever else. But ...
0
votes
0answers
14 views
Optimizing read I/O with read ahead while avoiding storing data in page cache
I need to be able to read data sequentially from a file while not storing the data that is being read in the page cache as the file contents are not expected to ever be read again and also because ...
1
vote
2answers
75 views
How to determine the status of my server
I would like to know how to determine the status of my server using the top command or if I have to change the server or add more resources. Next is the output the top command in my server.
Next are ...
0
votes
1answer
35 views
switch to root takes long time [duplicate]
I have a system (RHEL) and switching to root takes about 1 minute. (su - root)
However, switching to any another user takes less than 1 second.
Is there a way to debug, why does switching to root take ...
1
vote
2answers
26 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
28 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 ...
0
votes
0answers
23 views
XFS: is the fragmentation factor of our MongoDB replicaset alarming for performance?
We see those values on prod MongoDB nodes. Customer complains about performance and we found out it's disk I/O related
[root@mongodb-1 ~]# xfs_db -c frag -r /dev/vdatavg/mongodb_mms_datalv
...
1
vote
0answers
14 views
Does dstat captures disk i/o by the OS prefetching?
I ran a program which sequentially reads a big file.
The transfer rate [MB/sec] is strictly controlled by the application as 5MB/sec.
However, when I monitored the disk i/o bandwidth usage using ...
2
votes
1answer
32 views
Is there a way to split the encryption/decryption process on multiple core with SFTP?
I am in a case where the encryption process in an SFTP transfer maxes out one CPU core. However my IO bandwidth (disks, buses and network) is far from being maxed out.
That being said, the system in ...
1
vote
0answers
52 views
Discrepancy between shared memory from /proc/meminfo and ipcs
Running free -hm outputs:
total used free shared buffers cached
Mem: 15G 15G 389M 321M 169M 11G
-/+ buffers/cache: ...
0
votes
1answer
25 views
Load average for specific time with all programms
I'm searching for a linux tool to make some "performance tests". I have two (or more versions) of programms wihch do the same. To compare versions with each other I want to run these for a specific ...
4
votes
4answers
148 views
How can I optimize this Unix command?
The following command takes about 10 minutes to output the result
find . -name "muc*_*_20160920_*.unl*" | xargs zcat |
awk -F "|" '{if($14=="20160920100643" && $22=="567094398953") print $...
1
vote
1answer
68 views
How well does grep/sed/awk perform on very large files? [closed]
I was wondering if grep, sed, and awk were viable tools for finding data in very large files.
Lets say I have a 1TB file. If i wanted to process the text in that file, what would the time frame look ...
0
votes
0answers
142 views
why does gnome 3 lag in all distributions?
For some reason every single animation in gnome 3 lags a lot on my laptop (lenovo e330). I have tried the most recent version of a lot of different distros: ubuntu gnome, debian, centos, antergos, ...
0
votes
1answer
50 views
64GB Debian 8 Server, Do I need SSD?
I have a Debian 8 server with following config:
Quad Core E3-1270v5
64GB RAM
2x4TB SATA Disks
The server uses nginx 1.10 and redis to deliver files to clients. My question is since newrelic shows my ...
6
votes
1answer
234 views
How to benchmark different text processing commands and find out the fastest?
I have a text file and I need to process it according to some rules. To accomplish the task I can use multiple ways. For example I can use the linux command cut, paste, sed, awk etc. There are ...
0
votes
1answer
13 views
Severe Lagging on Wine and PlayOnLinux with openSUSE
I am having an issue with the performance of some older games. For example if I am trying to run Panzer General Forever or Panzer General 3D, I am facing extreme lagging on clicks and when moving the ...
1
vote
0answers
53 views
LVM mirror creates high load from time to time, how to lower these effects?
Or: How to throttle down one LVM mirror leg lowering its assumed synchronization cpu load?
Is it possible to tweak a LVM mirror configuration so it takes it easy on mirroring files?
Whenever there ...
0
votes
2answers
119 views
ethtool with virtual NIC shows nothing - print the current settings of the NIC in OpenStack VM
On a OpenStack VM I see only
# ethtool eth0
Settings for eth0:
Link detected: yes
On RHEV VM the same small output. Tried it on Ubuntu and RHEL7 VM.
I wish to see something like (the speed ...
