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Re: using swap when there is free ram


On Fri, Mar 01, 2019 at 02:39:22PM -0300, Bruno Schneider wrote:
> On Fri, Mar 1, 2019 at 2:18 PM Reco wrote:
> >
> > Please post the contents of /proc/meminfo. And "sar -r ALL 1 10", for
> > the sake of the completeness.
> $ cat /proc/meminfo
> MemTotal:        3975380 kB
> MemFree:         1886004 kB
> MemAvailable:    2307332 kB

Now that, ladies and gentlemen, is interesting.

> Buffers:           49840 kB
> Cached:           638404 kB

Especially combined with this.

> SwapCached:        28688 kB

And this.

> SwapTotal:        979928 kB
> SwapFree:         764888 kB

And this.

First, there's huge amount of unused (not to be confused with "free")
memory on your host. And no, it's not a filesystem's cache (600M), it's
really "nothing there"-unused memory which amounts 1880M.

Second, you do have *something* in the swap (220M give or take), yet
it's 28M of that which got swapped back.

Taking it all into the account, I propose the following scenario - not a
long time ago there was a process (or a couple of those). Was it the
browser, or something written in Java (or Python), or some kind of
Virtual Machine - is not relevant, but it did consume RAM. But it got
terminated, and what we're seeing here is the aftermath.

> There is no sar command on my system.

Consider installing it, the package's called sysstat.
Comes with useful diagnostic utilities of all shapes and colors, and
they *do* have a minimal resource consumption.

> > To prevent it:
> >
> > sysctl -w vm.swappiness=0
> >
> I just read some people arguing that 1 is better than 0 because the
> later means "never swap" while the former means "swap if out of RAM".
> I'll try 1 to see if it reduces swapping, thanks.

Whatever floats your boat. I use "10" personally, but YMMV.