How To: Adjust Swappiness

In today’s article, we’re going to learn how to adjust swappiness. It’s something you might want to do, as many don’t like the initial value set by the developers. It’s relatively easy.

I’ve written about swap before. I think you’ll find the best information in my recent article telling you how to remove a swap file. In that article, I tell you why I still use a swap file – even when I have lots of RAM available.

The reason for that boils down to how a swap file isn’t just some place that the kernel sticks things when you’re out of RAM. It has other uses as well. I figure I’m not smarter than the kernel and evidence tells me that the kernel uses swap even when there’s all sorts of RAM available. So, I use a swap file (not a swap partition these days). You might also want one if you plan on using advanced power management features like hibernation or sleep.

Anyhow, one of the only settings you can change regarding swap is the ‘swappiness’ value. That setting is basically how aggressively the kernel will use swap. The higher the number, the more the kernel will use swap. The lower the number, the less the kernel will use swap. It’s pretty basic in theory.

I don’t actually normally adjust the swappiness value. It works just fine at the default setting, so it doesn’t seem to me like I need to adjust it. Other people adjust it, and that’s fine. Either way, I’m going to tell you how to adjust the swappiness value. You do what you gotta do.

Adjust Swappiness:

This article requires an open terminal, like many other articles on this site. If you don’t know how to open the terminal, you can do so with your keyboard – just press CTRL + ALT + T and your default terminal should open.

With your terminal open, let’s see what value swappiness is set at before we decide to adjust swappiness. Enter the following command:

The default is usually 60, at least in the Ubuntu world, and some folks think that’s too aggressive. That value is easy enough to change. But, what I’d suggest doing is adjusting the value temporarily so that you can see what happens when you adjust swappiness. To set the value temporarily, you can just use this command:

Adjust the ’30’ to any number you want between 0 and 100. Both extremes are likely bad, but I’ve used values as low as 10. You could even set it to 0, which should stop the kernel from swapping anything.

Once you find a swappiness value you like, you can make it a permanent change to your system. That’s pretty easy. You just:

Add the following lines of text:

Use your own value if it’s not 30 and save the file. To save a file in nano, press CTRL + X, then Y, and then ENTER.

You can then reboot, or just wait until your next reboot, and the new swappiness value will be used. If you don’t feel like rebooting immediately, just adjust it temporarily and reboot when it’s convenient for you.

Closure:

There you have it, another article! This one has you learning how to adjust swappiness to a value that you can work with. I’d encourage folks to read the linked swap file article to see why I use a swap file even when I have gobs of RAM. If nothing else, using one won’t break anything.

Thanks for reading! If you want to help, or if the site has helped you, you can donate, register to help, write an article, or buy inexpensive hosting to start your own site. If you scroll down, you can sign up for the newsletter, vote for the article, and comment.

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Remove A Swap File

In today’s article, we’re going to learn how to remove a swap file. This isn’t something I recommend, for reasons I’ll explain, but I have no ethical qualms about telling you how to do so. After all, it’s your computer. You get to decide what it does!

There are some folks who will tell you that if you have enough RAM you don’t need swap. Well, I am not one of those people. I tend to have swap enabled regardless of how much RAM I have. I have a good reason and I’ll explain it to you as best as I can. I mean, the actual inner workings of the kernel are above my head, but I’ll explain it – or let other people explain it.

See, contrary to popular opinion, swap isn’t just a place the kernel sticks stuff when you’re running low on RAM. For example, check out the picture below:

swap in use with plenty of free RAM
As you can see, swap is used even with plenty of free RAM.

Here’s more information about the free command.

Now, do me a favor and go Google Linux and swap. You’ll find plenty of pages that briefly have this to say (and barely this to say):

Swap space in Linux is used when the amount of physical memory (RAM) is full. If the system needs more memory resources and the RAM is full …

                                                                                                        That’s from MIT!

That’s only about half the story… There’s more to it, and that is kinda important.

Some More About Swap:

So, is it really that simple? Of course it isn’t! If it was really that simple, the intro to this would have been so much easier to write. No, it’s slightly more, a bit more, complicated than that. See, let’s quote a more thorough (and accurate) Linux.com:

Swapping is necessary for two important reasons. First, when the system requires more memory than is physically available, the kernel swaps out less used pages and gives memory to the current application (process) that needs the memory immediately. Second, a significant number of the pages used by an application during its startup phase may only be used for initialization and then never used again. The system can swap out those pages and free the memory for other applications or even for the disk cache.

                                                                                                     –Emphasis Mine.

What can we take from that? Well, it’s not just a place where the kernel stuffs things when there’s no RAM left – it’s also a place the kernel sticks things to avoid wasting RAM. This is very different than swap is just a place where the kernel stuffs things when RAM is low. It avoids using some RAM that’s best used elsewhere. That seems kinda valuable and important to me. Again, the inner workings of the kernel are pretty much witchcraft to me, but swap seems like a good thing to me.

The kernel is pretty smart about this, from what I’ve observed. It’s good at its job. It’s better at its job than you are. It is better at its job than I am. I highly encourage you to use swap, saving your RAM for more useful things. With disk space as large as it is, you’re not going to miss a couple of gigabytes. Let the kernel do its job, managing RAM as best as it can. They’ve put thousands of hours into making the kernel smartly deal with RAM, there’s no reason to hobble it.

Of course, ain’t nobody gonna listen to me… So, with that said, I might just as well go ahead and tell you how to remove a swap file… You’re gonna do what you want anyhow!

Remove A Swap File:

This article requires an open terminal, like many other articles on this site. If you don’t know how to open the terminal, you can do so with your keyboard – just press CTRL + ALT + T and your default terminal should open.

The first thing we’re going to do is verify that you actually have a swap file…

If that mentions a swap file, only calling it a ‘swapfile’ (a single word), then your next step is to turn your swap off.

Now, for your next step you will want to remove the swap information from fstab, so let’s go like this to do that:

Find the line that starts with /swapfile and delete the entire line. All of it. Leave nothing behind. If you screw this up, your next boot may be an interesting exercise. The line is probably longer than it looks unless you’re using a terminal in full screen! Be sure to remove all of it. It should end with a 0, actually a 0 and then a tab and another 0.

Be doubly sure to remove the full line and then save your work. Then save it with nano. To do that, just press CTRL + X, then Y, and then ENTER. That’ll save it.

Finally, remove the swap file itself. That one is nice and easy, you just:

That should do it! If you’ve realized you’ve made a mistake and want to have a swap file, you can always add a swap file. (I’m pretty sure it should be ‘swapfile’, but the rest of the ‘net calls it ‘swap file’, so I’m going with the majority – even though the majority don’t even know what the damned thing does!)

Closure:

There you have it. You now know how to remove a swap file. If that’s what you want to do, you go right ahead and do it. Truth be told, assuming you’ve got enough RAM, it won’t necessarily break anything. You might not even notice it is gone. Still, I figure it’s better safe than sorry – and who am I to judge what the kernel wants?

Thanks for reading! If you want to help, or if the site has helped you, you can donate, register to help, write an article, or buy inexpensive hosting to start your own site. If you scroll down, you can sign up for the newsletter, vote for the article, and comment.

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How To: Create And Enable A Swapfile

Today’s article is about how you can create and enable a swapfile. It largely ignores the debate about whether a swapfile is needed or not, though I make it clear that this is something I prefer. I know that others will have different views, but I also make it clear why I enable it.

A swapfile, or swap partition, isn’t just where the OS crams stuff when it has run out of RAM. It’s more complicated than that. Sometimes, the OS knows where it wants to store cached items and prefers the swap partition or swap file.  The OS can put items in swap while freeing up RAM for other bits that need caching. 

To make it abundantly clear, you absolutely can use Linux without a swapfile. You can also use Linux with a swapfile. If you want to enable a swapfile, read on. I’ll touch on this a little bit later in the article.

Some Swapfile Background:

I have a modern, large SSD and more RAM than I’ll ever possibly use. I still want to use swap, in this case a swapfile. Imagine my dismay when I installed Lubuntu 20.04 and found there’s no swapfile available during the basic installation? (It’s there in 21.04 and proceeding versions.)

no swapfile
See? There’s nothing there!

I could have manually made a swap partition during installation, but that didn’t seem like something I wanted to do – and messing with manual partitioning can be tiresome and tedious. I knew I could enable a swapfile later, which is what I did.

Again, trying to avoid the debate – just sharing my reasoning; I have ample disk space and storage is cheap. If it has any chance of helping, it’s a small investment. I should also mention that swap is far more complicated than ‘a place where the kernel sticks stuff when there’s no more RAM left’. In fact, it’s a lot more complicated than that. It’s where the kernel pages content that’s seldom used, and it’ll happily use swap even when there’s plenty of RAM available.

Since the option to enable a swapfile isn’t there during the installation, we might as well learn how to add a swapfile to Ubuntu. It’s a pretty painless process. 

Is Swap Already Enabled?

You should first check to see if you already have swap enabled. The process is the same with both a swap partition and a swapfile. To check we first need to open your terminal emulator. You can do that by pressing CTRL + ALT + T.

Now, let’s check to see if you’ve already got some swap going on.

If the output of that command shows nothing but a new line, you have no swap. If it says anything else, you’ve got swap enabled already and this article is not one you need to read. As this article is only about a swapfile, it won’t be helpful for questions about a swap partition. This article also won’t tell you how to resize your swapfile, though you could put some pieces together and figure it out for yourself.

Let’s Make A Swapfile:

Seeing as you already have your terminal open from the previous step, you can just leave it open. That’ll make this easier. Start with this first command and work your way through the article – making sure to not skip any steps.

Why 8 gigabytes when I have ample RAM and an SSD? Because I don’t want to worry about it ever it again. I should be able to open up every app I have and leave them open for a month. You do you and decide how big you want it to be!

Now that we’ve allocated space for the swapfile, we need to set some permissions. We don’t want anyone and their kid brother writing to swap, we only want root writing to swap.

Next, we need to let the OS know that’s swap space, to be used as a swapfile.

Then you turn it on with:

And you now have swap in the form of a swapfile and it’s turned on.

Permanently Enable A Swapfile:

I suppose we should make this change permanent, as it’d be an unneeded step to have to do it every time the system reboots. To make this permanent, we need to edit fstab and nano is a good tool for this.

And add this at the bottom of that document:

Those are 0, the digit, in case the font here makes it confusing. And seeing as we’re using nano, you save your by pressing CTRL + X, then Y, and then ENTER

At the end of this exercise, you should have a swapfile that gets loaded on reboot.  You shouldn’t even have to reboot for it to effect, it should already be currently loaded and working. You can next edit the swappiness value, if that’s something you feel like you want to do – or have a reason to do. In Ubuntu, it is a default of 60. If you want to edit it, you’ll have to wait for another article.

Closure:

There you have it! We’re on the downhill side of this project and it’s an article about how you enable a swapfile. If you don’t use swap, that’s fine. This article is for those who do want to use swap.

Thanks for reading! If you want to help, or if the site has helped you, you can donate, register to help, write an article, or buy inexpensive hosting to start your own site. If you scroll down, you can sign up for the newsletter, vote for the article, and comment.

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