[ale] adding swap? was "that same darn NFS problem SOLVED"

[Michael D. Hirsch]

On Monday 17 February 2003 02:53 pm, ChangingLINKS.com wrote:
> That is a great idea! My server gets crushed by a program that I call
> LINKER. LINKER makes multi-threaded connections to the Internet and
> collects data. Of course, while it is collecting the data, some of the
> web sites that it collects data have connection errors.
>
> I had two programmers look at the software, and it seems to bottleneck
> at the nic card. I can open another session and run as many as 2 more
> instances of the program - but usually the server gets sluggish (insofar
> as gettting results) at 2 instances.
>
> While that is going on, I can open 2 more instances on two more servers,
> and all of them seem to run at full speed - so it doesn't seem to be a
> data transfer problem.
>
> This is why I was adding 2 nics to the server. This is also why I think
> it may be a good idea to double my swap?
>
> How do I run a test to see whether more swap is needed?
>
> I have 512RAM, and 1019 swap(I think).

Well, if you notice that your swap is running low you might need more swap.  
More likely you need to fix a memory leak in your program.  Would you 
expect LINKER to use a gig of RAM?  That's an unusually large number.

The command "free", or the top command will show you your memory usage.  If 
you are using lots of swap you either have lots of processes, or some few 
processes consuming too much RAM.  Try sorting top's output by memory ('M' 
is the command for that) and see what process is sucking RAM.

Michael

> Drew
>
> On Monday 17 February 2003 1:38 pm, Michael D. Hirsch wrote:
> > On Monday 17 February 2003 02:30 pm, Chris Ricker wrote:
> > > On Mon, 17 Feb 2003, James P. Kinney III wrote:
> > > > With a 2.4.x kernel and RAM <=4G swap=2xRAM
> > >
> > > That's not necessary. There was a bug in early 2.4.x that required
> > > swap=2xRAM for decent performance, but that's long since been
> > > fixed...
> > >
> > > You need enough swap to hold your working set. That could be
> > > anything from no swap to gigabytes, depending on what you do on that
> > > system....
> >
> > Right, but the rational I heard is
> >
> > 1.  Having swap doesn't hurt
> > 2.  Unless you have so many processes and so much swap space that you
> > get swap bound
> > 3. swap = 2 x RAM is a reasonable heuristic.  If you use much more
> > than that you are probably swap bound, but up to that amount could
> > really happen without getting swap bound.
> >
> > Obviously one can create loads that would be usable with more than
> > that much swap in use.  One could also create loads that are unusable
> > with less than that much in use.  It is just a rough guess that often
> > works okay, and few of us have the time or ability to really do an
> > analysis of our swap needs.
> >
> > Michael
> > _______________________________________________
> > Ale mailing list
> > Ale at ale.org
> > http://www.ale.org/mailman/listinfo/ale

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