LinuxQuestions.org
Welcome to the most active Linux Forum on the web.
Go Back   LinuxQuestions.org > Forums > Linux Forums > Linux - Distributions > Red Hat
User Name
Password
Red Hat This forum is for the discussion of Red Hat Linux.

Notices

Reply
 
Search this Thread
Old 10-21-2007, 03:07 AM   #1
Maria
LQ Newbie
 
Registered: Oct 2007
Posts: 1

Rep: Reputation: 0
Question How to increase disk cache and maximize RAM usage?


Hi,

I'm running Red Hat Entreprise 3 on core 2.4.21-47Elsmp, on 6 hardware identical machines. They should also be configured identically, but I have reason to suspect they are not.

I'm working on a time-critical application, using the NI DAQ boards. When I verified my program at home, I had no problems, but when running them on 4 of the other identical machines, it showed errors that we didn't read the buffer fast enough. I'm using the Ni DAQmx drivers, that copy the FIFO from PCI-connected DAQ boards through DMA, with even intervalls. It then sends a callback function to my program to read the DMA buffer. It is this reading from the DMA buffer that is taking too long time.

My application is running 6 independent C-threads, controlled by a Python script. I know the python script is not the problem, since I've verified by running the 6 C-binaries without the script, letting the OS control them.

All the machines are running with 3GHz and have 2 GB RAM. On my home machine where the application is working, I can see that 1,5 GB is used as disk cache. Also the free command shows that we are using up over 90 % of the RAM, which is good.

On the 4 machines where I get timing problems, I see that only 15 % is used as disk cache and overall, only 30 % of the RAM is used.

I have a sixth machine that works almost ok, and that one has a disk cache of 650 MB and uses 75 % of the RAM.

Using the RAM for disk cache speeds up the application.

All the settings under /proc/sys/vm are identical between the machines.

What configuration can differ? Is there any setting missing? I'm really stuck and would appreciate all the help I can get.

Waiting for your reply!
Maria
 
  


Reply

Tags
cache, disk, increase, performance, ram, speed


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
Linux cache/buffers never increase DukeLeto Linux - General 1 01-02-2007 12:02 AM
Disk Cache Usage - slack10.1 on laptop -=Graz=- Slackware 2 04-25-2006 07:04 AM
increase free physical memory, decrease disk cache efm Linux - Hardware 4 03-30-2006 10:53 AM
Ram wiht suse, cache Disk cache??? fadelhomsi Linux - Newbie 2 02-06-2006 12:29 AM
Problems with disk cache and ram xvanhessianx Linux - General 5 03-19-2005 08:42 PM


All times are GMT -5. The time now is 02:53 AM.

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
identi.ca: @linuxquestions
Facebook: linuxquestions Google+: linuxquestions
Open Source Consulting | Domain Registration