LinuxQuestions.org
Welcome to the most active Linux Forum on the web.
Go Back   LinuxQuestions.org > Forums > Linux Forums > Linux - Software
User Name
Password
Linux - Software This forum is for Software issues.
Having a problem installing a new program? Want to know which application is best for the job? Post your question in this forum.

Notices


Reply
  Search this Thread
Old 10-29-2013, 05:11 PM   #1
Consystor
LQ Newbie
 
Registered: Jul 2003
Location: Germany (BW)
Posts: 23

Rep: Reputation: 0
Question Maximum CPU utilization during reads/writes from/to fast drives


Hello together!

I've a system with 8 SSDs (each ~500MByte/s read/write) connected to a LSI 9271-8i RAID-controller as a RAID0 array.
Under Windows I get write and read rates of about 4GByte/s.

Under Linux I test for example with
time dd if=/dev/zero of=/dev/sdX bs=1M count=8000
but then I only get this:
8000+0 records in
8000+0 records out
8388608000 bytes (8.4 GB) copied, 7.61166 s, 1.1 GB/s

real 0m7.613s
user 0m0.000s
sys 0m7.572s

So the rate is too low and the reason seems to be the CPU utilization because dd is running on one core and its "system utilization" is at 100% during the whole runtime.
If I run 12 dd in parallel and write to the same device then the aggregated rates are ~3GByte/s.
The utilization of the benchmark bonnie++ is also ~100%.

Hence I've these questions:
  • Is there a way to get rid of this CPU-limitation during reads/writes?
    I mean: The system has 2 processors with each 6 cores. So if dd uses write() or a similar call, is there no "paralelized version" under linux?
  • Is there a benchmark which generates multiple threads/processes for concurrent reads/writes?

Many thanks for any help!

Last edited by Consystor; 10-29-2013 at 05:14 PM.
 
Old 10-29-2013, 05:16 PM   #2
jefro
Moderator
 
Registered: Mar 2008
Posts: 20,452

Rep: Reputation: 3268Reputation: 3268Reputation: 3268Reputation: 3268Reputation: 3268Reputation: 3268Reputation: 3268Reputation: 3268Reputation: 3268Reputation: 3268Reputation: 3268
dd is a poor way to test it no matter how you set it up.

Use some other method.


Might look at how you set up the raid, lsi driver, kernel settings, swap file or swap partition too, filesystem may be most important too for the size of files you are trying to move. We'd need to know some of that.

Might look at iozone too.

I'd welcome others thoughts on this too.

Last edited by jefro; 10-29-2013 at 05:22 PM.
 
Old 10-29-2013, 05:28 PM   #3
Dman58
Member
 
Registered: Nov 2010
Location: The Danger Zone
Distribution: Slackware & everything else in a VM
Posts: 293

Rep: Reputation: 31
What software are you using in Windows to do your testing? Try getting a Linux equivalent in order to get a more accurate reading.
 
Old 10-29-2013, 05:37 PM   #4
Consystor
LQ Newbie
 
Registered: Jul 2003
Location: Germany (BW)
Posts: 23

Original Poster
Rep: Reputation: 0
@jefro
I write directly to the device and I don't use any filesystem.
And I know that I must use another method. That's why I've created this thread.
The kernel is one from debian but it doesn't matter. I get same results with ubuntu kernels.

@dman58
Under Windows I use "ATTO Disk Benchmark".
And my second question is about an "equivalent benchmark" because I don't know one for linux that isn't CPU-limited on such fast drives.

Last edited by Consystor; 10-29-2013 at 05:45 PM.
 
Old 10-30-2013, 05:03 AM   #5
syg00
LQ Veteran
 
Registered: Aug 2003
Location: Australia
Distribution: Lots ...
Posts: 19,390

Rep: Reputation: 3426Reputation: 3426Reputation: 3426Reputation: 3426Reputation: 3426Reputation: 3426Reputation: 3426Reputation: 3426Reputation: 3426Reputation: 3426Reputation: 3426
Use a multi-threaded capable tool - fio, dbench (maybe), iozone ...

Phoronix does truckloads of benchmarks, and tell you what they use - might be a good place to start looking.
 
  


Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off



Similar Threads
Thread Thread Starter Forum Replies Last Post
High Run queue utilization although CPU utilization is low.. rajeprag Linux - Server 0 08-18-2013 10:44 AM
Java File reads and writes manolakis Programming 2 04-08-2009 01:52 PM
Linux desktop GUI tool for CPU utilization and bandwidth utilization karimasif Linux - Software 4 03-03-2008 02:09 PM
CD R/RW: reads or writes but not both hatha Linux - General 6 04-17-2005 08:12 PM
cdburner reads not writes NGraphiX Linux - Hardware 1 02-28-2003 05:29 AM

LinuxQuestions.org > Forums > Linux Forums > Linux - Software

All times are GMT -5. The time now is 04:38 PM.

Main Menu
Advertisement
My LQ
Write for LQ
LinuxQuestions.org is looking for people interested in writing Editorials, Articles, Reviews, and more. If you'd like to contribute content, let us know.
Main Menu
Syndicate
RSS1  Latest Threads
RSS1  LQ News
Twitter: @linuxquestions
Open Source Consulting | Domain Registration