Page Fault + Memory

Thread Tools Search this Thread
Top Forums UNIX for Dummies Questions & Answers Page Fault + Memory
# 1  
Old 06-03-2011
Page Fault + Memory

I am not sure where to post this so i will put it in the newbie section.

I have set up a bog standard debain 6, LAMP environment in the cloud.

The specs

1 core at 2GH
2.5gb Memory

running Jommla, with about 1.6K visitors a day.

I am using AppFirst ( to monitor the server, and I am getting memory usage over 956M alerts almost every hour (not at the same time)

I have had a look at their monitoring tools and I can see the following.

1. At the times of the alerts the Page Faults go up very high.

2. The number of process goes up really high (i assume this is what is causing the page faults).

3. Most of the page faults are associated with apache.

I intialy thought it was the database , as joomla is bit database heavy sometimes.

However I am not sure now and I need some pointers.

I have no swap space defined on the disk, I totally forgot about this when setting it up.

Any kind of help would be good, the memory spikes may have nothing to do with the page faults but I think it does.
# 2  
Old 06-03-2011
Since you have no swap, it is all from mmap()'d pages like libraries but can be any file with any app using mmap()/mmap64(). Page faults are not toxic, sometimes you can find an app that stirs things up unnecessarily and get rid of it, else buy more RAM.

You can make swap after the fact, by creating a big file and assigning it as swap. I would expect it is good for system stability to have some, if not lots. Some like to buy SSD for swap, but I am not sure as it is not churn friendly.
# 3  
Old 06-03-2011
Mostly, page faults are when a process uses memory it hasn't needed before and the operating system goes "Hmmmm, I haven't actually given you that memory yet, hang on" and makes the process sleep a moment while it hunts up more memory for it.

It could also be happening when the system's low on memory and swapping, but since you don't have swap, that's not relevant.

It's possible to add swap even if you forgot to partition it, by creating a large, empty file, running mkswap on the file, and mounting the file as swap.

I'm still not sold on the idea of SSD's myself. There's a world of difference between "This mechanical disk will work for at least a year no matter how the software abuses it" and "every single write you do to your SSD slowly, inexorably kills it, but our algorithm spreads the damage enough it's unlikely to be problem."
Login or Register to Ask a Question

Previous Thread | Next Thread

9 More Discussions You Might Find Interesting

1. Solaris

M4000 Memory Fault

Hi Guys and Gals, Does anyone know how to track down a faulty DIMM on the memory board of an M4000? showhardconf tells me which board it is, but was wondering if there was a way to track it down to a DIMM? Thanks in advance Martin (5 Replies)
Discussion started by: callmebob
5 Replies

2. Linux

Help with memory fault

We have migrated our application from HP UX to linux. The code is in 4gl and after migration it has started giving Memory fault while running a batch job. The trace shows segmentation fault after a series of recvfrom and sendto(DB read) sigsegv segmentation fault @ 0 0 killed by SIGSEGV The... (2 Replies)
Discussion started by: aimee
2 Replies

3. UNIX for Advanced & Expert Users

Page fault in kernel

I have a query (Don't know whether its the right folder to ask) ................. What happens when page fault happens in Kernel ..(as the kernel mode is non-preemptive)... any guesses... Thanks in advance (2 Replies)
Discussion started by: yash0101
2 Replies

4. Linux

page fault handle

For zero-copy communication among the processor, I allocated a pool in the kernel. From user space, it may mmap the virtual memory device into user space i.e 0x80000000. the client may send a message to the server, it may request a buffer, kernel will allocate a block for it and register it into... (0 Replies)
Discussion started by: a2156z
0 Replies

5. UNIX for Dummies Questions & Answers

mysql memory fault

I (think I) installed MYSQL on a Red Hat box. When I try to start mysql I get a memory fault error. Any ideas on how to fix this? Here is some info that might help: My distro info $ cat /proc/version Linux version 2.4.21-40.ELsmp (bhcompile@hs20-bc1-7 (gcc version 3.2.3... (0 Replies)
Discussion started by: wsetchell
0 Replies

6. Solaris

Page Fault very high

Hi, We are running SUN sparc 5.8, notice frequent "Page Faults" message from our monitor s/w "ServerVantage" coming but no message display in SUN syslog or messages log. Any ideas why or what to check? thanks, Ahmad (2 Replies)
Discussion started by: Ahmad
2 Replies

7. Programming

memory fault

When I excute a program . It seems to generate an error : memory fault (core dump ) So how can i (1 Reply)
Discussion started by: iwbasts
1 Replies

8. HP-UX

Data page fault

What causes 'page data fault' or 'data memory protection fault' under HP-UX 11. The server crashes and the shutdownlog reports the above error. For your info, Oracle 8i is running . Appreciate your fast response, Wobitu :confused: (2 Replies)
Discussion started by: wobitu
2 Replies

9. UNIX for Dummies Questions & Answers

Memory Fault

I am using Unix OpenServer Release 5. When a run a application with user different to "Superuser" the application give me the following error: "Memory Fault - Core Dump". What's that mean? Thank you in advance. Roberto Veras. (1 Reply)
Discussion started by: robertoveras
1 Replies
Login or Register to Ask a Question

Featured Tech Videos