[uml-devel] x86_64, TT mode, no tmpfs - steadily growing number of threads

[uml-devel] x86_64, TT mode, no tmpfs - steadily growing number of threads

[William Stearns]

Good afternoon, all,
 	With a FC2 x86_64 host with no skas patch (stock RH kernel) and no 
tmpfs, I find that a 2.6.6 uml vm (happens to be i386 slackware) keeps 
getting more and more pids out on the host.  By mounting /tmp as tmpfs, 
this effect goes away; the vm stays around 140 pids and doesn't appear 
to grow any further.
 	When the PID leakage(?) was happening, I would usually contact the 
owner of that VM once it was up around 8,000 host pid's and was occupying 
around 4G of ram so we could recover all of those.  :-)
 	The reason why I didn't have tmpfs mounted on that host was that 
uml.ctl ends up there and for some reason I could not get networking to 
work on x86_64 when /tmp was mounted tmpfs.  By convincing uml_switch and 
the vm itself to use /var/tmp/uml_ctl, networking worked again.
 	Cheers,
 	- Bill

---------------------------------------------------------------------------
 	"First rule: Never sweat the petty things, or pet the sweaty things."
(Courtesy of "Michael J. Dark" <darkmich@zebu.cvm.msu.edu>)
--------------------------------------------------------------------------
William Stearns (wstearns@pobox.com).  Mason, Buildkernel, freedups, p0f,
rsync-backup, ssh-keyinstall, dns-check, more at:   http://www.stearns.org
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[uml-devel] Re: x86_64, TT mode, no tmpfs - steadily growing number of threads

[Jeff Dike]

On Thu, Jun 16, 2005 at 03:49:43PM -0400, William Stearns wrote:
> Good afternoon, all,
> 	With a FC2 x86_64 host with no skas patch (stock RH kernel) and no 
> tmpfs, I find that a 2.6.6 uml vm (happens to be i386 slackware) keeps 
> getting more and more pids out on the host.  By mounting /tmp as tmpfs, 
> this effect goes away; the vm stays around 140 pids and doesn't appear 
> to grow any further.

From the usage of an x86 filesystem, I gather that this is the 2.6.4 UML
that has the compatibility code in it.  No idea why it's leaking processes
(nor am I too interested in figuring it out unless it's still happening :-).

> 	The reason why I didn't have tmpfs mounted on that host was that 
> uml.ctl ends up there and for some reason I could not get networking to 
> work on x86_64 when /tmp was mounted tmpfs.  By convincing uml_switch and 
> the vm itself to use /var/tmp/uml_ctl, networking worked again.

You can specify the sockets you want uml_switch to use.  /tmp is just the
default.

				Jeff


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