intr using Swap

[hiren panchasara]

On 02/17/16 at 04:44P, Efra?n D?ctor wrote:
> El 17/02/2016 a las 01:15 p. m., dweimer escribi?:
> >
> > They may not show as swapped unless the entire process is actually 
> > swapped, which would be unlikely to occur. Personally I wouldn't worry 
> > about it, the only thing I can think of is to restart processes one at 
> > a time to see which one clears up the swap usage. Granted you may see 
> > a little clear after each process.
> >
> > The more important task would be to determine what caused the memory 
> > to run out in the first place, and decide if its going to be a 
> > frequent enough occurrence to justify adding physical memory to the 
> > system.
> >
> > There is likely some way to find out what is using it, but that is 
> > beyond my knowledge.
> >
> > -- 
> > Thanks,
> >    Dean E. Weimer
> > http://www.dweimer.net/
> 
> The server has 64 GB of RAM, 40-45 GB are always inactive thats why I'm 
> wondering why are the processes being swapped out.

Yes, I've seen this too. Inact end up accumulating a very large chunk of
memory leaving Free to very low. 

What VM/pagedaemon seems to care about is Free+Cache and not just Free.
I kind of get that Free mem is wasted mem but putting everything in Inact
to the point that machine has to go into swap when a sudden need arises
also doesn't seem right.

I guess it all boils down to adjusting defaults to the system's need.
i.e. if you know you have a proc that may need a large chunk of mem
you'd need to tweak free+cache target accordingly. What I find lacking
is the correct/easy way to do it. If I look at available sysctls:
vm.v_free_min: Minimum low-free-pages threshold
vm.v_cache_min: Min pages on cache queue
vm.v_free_target: Desired free pages
And I cannot get them to do the right thing to have more Free around so
swapping doesn't happen in sudden need. And are these all runtime
sysctls? OR does it require reboot for them to work right? 

Anyways, enough rant from someone who doesn't know much about VM. :-)

Cheers,
Hiren
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