Memory leaks in Ubuntu?

[Michael Butash]

So I've been digging into learning more about the virtual memory
subsystem of 2.6 kernels, and I found a bunch of interesting info here I
figured I'd share that was helpful:

http://www.redhat.com/promo/summit/2008/downloads/pdf/Wednesday_1015am_John_Shakshober_and_Larry_Woodman_Decoding_the_Code.pdf

So based on what Matt recommended, I began looking at some of the ubuntu
kernel defaults and found they do differ somewhat from stock and/or
redhat's, but actually in such a way that it *should* help my issue, but
is not.  For instance, this doc recommends lowering *dirty* pagecache
ratios to have have pdflush remove them more often, but this doesn't
necessarily occur, or at least not in my case.  This could be because my
memory usage isn't exactly *dirty*, and /proc/meminfo tends to indicate
this showing very little dirty paging.

I tried setting these in sysctl.conf to see if it helped clean up after
the inactive memory, but nothing particularly changed going higher to
Redhat's defaults or lower than Ubuntu's defaults:

vm.swappiness = 0
## rh default ## vm.dirty_ratio = 40
## ubu default ## vm.dirty_ratio = 10
vm.dirty_ratio = 8
## rh default ## vm.dirty_background_ratio = 10
## ubu default ## vm.dirty_background_ratio = 5
vm.dirty_background_ratio = 2

Now I'm wondering just wtf is claiming memory and letting it go
inactive, and just how I can get linux to automatically reclaim this.  I
did find a sysctl to forcibly dump the pagecache that actually purged
everything, and reclaimed my memory.  While this is flippin great, as
just maybe I won't have to kick it like a Win98 box periodically, I
really can't imagine there's nothing to wipe it's own butt.  I suppose I
could do a cron job to do so, but not really sure what adverse effect
it'll have.  Running it with a ton of things running didn't seem to have
any effect, but not sure long-term this will do, or in critical
situations potentially.

Guess I'll keep digging, but at least I have a workaround for now...

Thanks for everyone's input!

-mb


On Thu, 2009-08-06 at 10:06 -0700, Matt Graham wrote:
> From: Michael Butash <michael at butash.net>
> > Meh, I've had too many ati cards die and freak out my systems,
> > which is what drove me to NV.  I haven't had one NV die, but
> > obviously comes with other issues...
> 
> The problem may not be with the nVidia card, but with the Ubuntu
> kernel itself.  Debian and Debian-derived distros have a serious
> Free bias, and distro kernels have more weird bugs than the vanilla
> kernels do.  The first thing I'd try is to install a vanilla kernel
> on the box, then recompile the evil binary-only nVidia modules
> against that kernel.  I've been doing this since the nVidia modules
> were beta and XFree 3.3.6 was the latest thing, and I've never had
> a problem with X eating all the memory.
> 
> I don't do a whole lot of OpenGL use or TV watching, though, so YMMV.
>