Re: "adjusting" / control Swapping

[Johnny Billquist <bqt%softjar.se@localhost>]

Greg Troxel wrote:
> "Niels Dettenbach" <nd%syndicat.com@localhost> writes:
>
> > volume of 5 GB swap. The swap is needed as there are peaks of required
> > memory sometimes (once or twice a month) where the system stops with
> > out of mem otherwise. In most time the swap is not required, but used
> > (I assume i.e. for file caching). If i restart several of that
> > mem-pigs / deamons (i.e. once a day) within the system the swap was
> > wiped out and the sytsm seems to run faster (with less load). There
> > are daemons who doenst offer control of their caching or mem-usage
> > behaviour byself.
>
> As others said, your problem is badly-behaved daemons.  Daemons that
> intend to run forever should not accumulate memory usage.  So if they
> do, add a cron job to restart them daily.
>
> If it's apache, you might try an hourly reload and a daily restart.
> apache might be ok but with embedded python it can get leaky.  reload is
> nice in that child server processes are allowed to finish and new ones
> are started, but the main process remains, so there is no losss of
> service.  However it does not recover from leaks in the main process.

I'm not totally convinced the problem is badly-behaved daemons. If you 
have something that exercises the file caching a lot, your daemons will 
be pushed out to swap, even if they behave nicely. Killing them will of 
course remove them from swap. Restarting them will once more place them 
in memory, throwing away some file caches instead, since they are older.

Thus observing the same pattern, even though the processes are behaving 
nicely.

Personally, I have the following in my /etc/sysctl.conf on just about 
any machine I run:
vm.filemin=5
vm.filemax=10
vm.anonmin=5
vm.anonmax=80
vm.execmin=5
vm.execmax=50
vm.bufcache=5

not saying that this is ideal for all situations, but it much improved 
the systems for me at the time I was hunting around this thing, many 
years ago... I've left it at that since then, and it still produces a 
more responsive system in my experience.

        Johnny