wtb

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Hi all,


On one hand there is the swap partition but on the other hand, is there any pagination file for the virtual memory under RHEL 4.6 ?

Like under Windows, there is a swap file growing in the course of using applications.

If this file exists, and I think that it exists, where is it ? And someone can tell me how to increase or reduce the size of this file ?


Thanks !



PS : Sorry for my bad english.

anomie

The swap partition serves the same purpose as a page file. It is a fixed size (created by you), but you can expand it or reduce it using various methods. Normally, you shouldn't need to do that.

Explain more about your situation if you need specific help.

johnsfine

If you choose, you can use a swap file instead of or in addition to a swap partition.

Having the swap file grow on demand is one of the bad features of Windows and one of the reasons Linux memory management is more efficient and more reliable.

A swap file that grows automatically as it is used is significantly more complicated than one whose size is fixed. It is a feature that could be done well by an expert OS programmer, but in Windows it was not done well and so far as I understand, in Linux it was not done at all.

In Linux, you need to decide on the amount of swap space.

DrLove73

Maybe skilled programmer could automatically mount next swap file if active swap partition or file is running full.

anomie

@DrLove73: Possibly so. But if that's your reality, you should invest in more RAM.

syg00

"swapon -s" will show the currently in-use swap extents.
Redhat have (or had) some documents on their site to walk you through adding/reducing swap space. Several scenarios need to be catered for.
As for dynamically adding, merely (always) activating extras is sufficient - kswapd will by default fill each in turn as needed unless told otherwise.

DrLove73

I do not need it. 2GB is enough for my needs. I do not recall last time I've seen my PC used swap. I was giving a possible solution to wtb .

wtb

Thanks for the answers.

I made a research in Redhat documentation with the elements you gave me and I found that there are different ways to modify swapping.


1. Create a new swap partition
2. Create a new swap file
3. Extend swap on an existing LVM2 logical volume


RH recommends the option 3. But to do it you must have a LVM logical volume or need to create one. I think it's probably the best option but not the more easy to do.


For those who are interested, this is the procedure for the creation of a swap file :

# dd if=/dev/zero of=/swapfile bs=1024 count=524288
# mkswap /swapfile
# swapon /swapfile

add this line in /etc/fstab to enable the partition at boot time :
/swapfile swap swap defaults 0 0


source : swap-creating-file.html

syg00

There is no point installing LVM just for swap - if you have a vg with space, use that. Else just create partitions/files in your current setup. Despite what you might read on the net, there is no adverse effect in using swap files rather than swap partitions with 2.6 kernels.

wtb

Yes you're right syg00, thanks for your answer. I'll try with a swap file to begin.