On Tue Feb28'23 08:09:24PM, Jeffrey Walton wrote:
> From: Jeffrey Walton <noloader@xxxxxxxxx>
> Date: Tue, 28 Feb 2023 20:09:24 -0500
> To: Community support for Fedora users <users@xxxxxxxxxxxxxxxxxxxxxxx>
> Reply-To: noloader@xxxxxxxxx, Community support for Fedora users
> <users@xxxxxxxxxxxxxxxxxxxxxxx>
> Subject: Re: recommended partition for swap with 0.5 TB memory
>
> On Tue, Feb 28, 2023 at 3:02 PM Ranjan Maitra <mlmaitra@xxxxxxx> wrote:
> > On Tue Feb28'23 01:56:08PM, Richard Shaw wrote:
> > > On Tue, Feb 28, 2023 at 1:43 PM Ranjan Maitra <mlmaitra@xxxxxxx> wrote:
> > >
> > > > I am trying to install Fedora on to a new machine that has 0.5 TB RAM.
> > > > Hard drives are 256 GB for / and friends, and 2 TB for /home partition. In
> > > > the past, it used to be suggested that swap be twice that of RAM: this
> > > > later changed to the same amount, and now it is very unclear (to me)
> > > > because I have not tracked the latest recommendations. Anyway, what would
> > > > you suggest? The machine is a Dell Precision 7920 with 28 cores/56 threads.
> > > >
> > >
> > > By 0.5TB you mean 512GB of ram? Assuming you're installing Fedora 36 or 37,
> > > I would just leave the defaults alone, which utilizes swap on zram. So
> > > basically it won't use any swap unless needed. You can adjust the amount of
> > > memory allowed to be used for swap.
> >
> > Right, thanks. So, I let the installer pick this up. I usually do a custom partitioning, does that mean that I do not declare anything for swap?
>
> And set swappiness to something low, like 1. There's almost no reason
> to allow anything to spill into the swap file with 512GB of RAM.
Agreed, but there are 56 threads on this machine. So, if all of them are being used, then the amount of memory is not that much on the average, though I hope to be fine.
I currently have a 8y-old 10C (20 thread) machine (originally with 32 GB, went up to 64 GB). At least for some jobs, I was not able to use all threads because of memory requirements. For that machine, I have:
$ swapon NAME TYPE SIZE USED PRIO /dev/zram0 partition 8G 0B 100 /dev/sdc6 partition 46.6G 0B -2
and
$ free
total used free shared buff/cache available
Mem: 65762928 1089656 61769992 30928 2903280 63914968 Swap: 57215992 0 57215992
so I guess there is the zram0 there.
I also don't see much value in having a lot of swap, unless it is some sort of very short (to be useful) holding operation (that is how my layman's mind likes to think about it).
>
> In fact, my daily driver has 64GB of RAM, and I set the swap file size
> to 4 GB and set swappiness to 1. The 4 GB swap is there for
> emergencies, but I don't think it's ever been needed.
>
Thanks again!
Ranjan
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