[Samba] Clearcase, Samba, and mnode values

[Jeff Layton]

On Thu, 8 Sep 2011 10:14:47 -0700
Kathy <banshee135 at gmail.com> wrote:

> That's possible and yesterday I was looking at possibly using Valgrind
> to see if I could dig further into that idea.  I've never used it
> before, though, so not sure if there is an easier method to detect
> kernel memory leaks.
> 
> And about static things in swap, I agree.  I have noticed on our old
> Clearcase/Samba server, that it consumes all the memory down to about
> 150M plus 72k of swap and just sits there like that.  Seems to be fine
> and can run for 2 months or longer like that.  That server, though,
> has only 4 gigs of memory and so I was assuming that it did that
> because it didn't have a lot of memory.  However, this new Clearcase
> server, which has 32 GB of memory appears to perhaps want to do the
> same thing.  So I began to wonder if that is just normal behavior --
> i.e., it caches all its memory.  But I think it's a problem because
> people started to report Clearcase running really really slow when it
> got down to almost nothing left and it just seems odd that it would
> consume all 32 GB of memory in less than 12 hours.
> 

That's normal. Linux will use up as much free RAM as it can to cache
file data, based on the principle that free RAM is wasted RAM. What
really matters is not free RAM, so much as *reclaimable* RAM.

If the memory is clean (meaning that it doesn't have data that needs to
be written back out), then the kernel can just free it on a
least-recently-used basis when the need arises. If not, then the kernel
will require more active participation to free up memory, which is
comparatively slow.

I think you'll probably need to step back and determine what the
application is doing when it becomes slow. It may very well be that
there is a problem with memory allocation at that time that's causing
the slowdown. But, you can't really assume that or you might end up down
a rabbit hole that has nothing to do with the real problem. Determining
that will probably require help from IBM as only they have real insight
into clearcase -- it's a closed source program, after all.

Either way, it's highly doubtful that this has anything to do with
samba.

-- 
Jeff Layton <jlayton at redhat.com>