To swap or not to swap ;-) (was RE: To lvm or not to lvm)

[Stephen Partington]

I have found some applications use sawp with direct calls.

"A significant number of the pages referenced by a process early in its
life may only be used for initialisation and then never used again. It is
better to swap out those pages and create more disk buffers than leave them
resident and unused."

On Sep 22, 2018 7:14 PM, "Michael Butash" <michael at butash.net> wrote:

I've run without swap while having 32gb of ram prior, and found things
would just be weirdly lagging at times without it.  Adding a swap partition
removed that, never really found out why.  Now I just always add a small
swap slice (usually 3-4gb) even if setting swappiness to minimum.

I never do suspend/hibernate or anything to swap, as I often have big
enough ram that it chewing into ssd space for it wasn't an option.  I just
sleep the laptops, and my desktops are never really powered down to bother
either.


-mb

On Sat, Sep 22, 2018 at 8:25 AM Bob Elzer <bob.elzer at gmail.com> wrote:

> > 4 - not having swap seems to make some things not work too well
>
> Swap depends on how much memory you have and how much memory your programs
> need.
>
> Back in the day when ram was less than a gig we would use 2 to 3 times the
> ram size for swap. You would add up the number and size of your programs
> you needed to run and give it that extra swap knowing that when swapping
> started it would slow things down some.
>
> Nowadays you can have 32, 64, 128gb and more ram.
>
> Programs are also bigger, but you still figure how much memory the
> programs take and add them all up and compare that with your actual ram.
>
> If you have 32gb of ram and only read mail and only browse google and
> PLUG, then you wouldn't really need any swap. But if you keep hundreds of
> tabs open, and have a huge memory resident database, and edit images and
> video, you may want to have swap.
>
> If you have 4-8gb of ram I would think 3 to 4 times that for swap.
> 16gb ram 1 to 2 times swap.
> 32 or more 1 times, depending on what you're doing maybe more.
>
>
>
> On Fri, Sep 21, 2018, 1:08 PM Carruth, Rusty <Rusty.Carruth at smartm.com>
> wrote:
>
>> So, in my limited experience with swapping, here's my conclusions:
>>
>> 1 - one big (that is to say, at least your ram size, and possibly 2x your
>> ram size) swap PARTITION is needed if you want to hibernate or suspend, and
>> I think it has to be the first one in your fstab (but I'm not sure on that)
>>
>> 2 - swap files work fine, but can't be used for suspend/hibernate.
>>
>> 3 - suspend/hibernate doesn't work with multiple partitions if (the first
>> one I think) isn't big enough to hold everything, even if the total swap
>> space is plenty big.
>>
>> 4 - not having swap seems to make some things not work too well, even
>> when you're not overflowing in to swap.  This one I don't have proof for,
>> but it just felt like a no-swap system ran in to walls sooner.
>>
>>
>>
>>
>>
>> -----Original Message-----
>> From: PLUG-discuss [mailto:plug-discuss-bounces at lists.phxlinux.org] On
>> Behalf Of Matt Graham
>> Sent: Friday, September 21, 2018 9:35 AM
>> To: Main PLUG discussion list
>> Subject: Re: To lvm or not to lvm
>>
>> ....  You might even be able to get away without swap if you don't want
>> to do suspend-to-disk.
>>
>>
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