Date: Tue, 15 Nov 2005 11:08:20 -0600
From: "Serge E. Hallyn" <serue@us.ibm.com>
To: Greg KH <greg@kroah.com>
Cc: Paul Jackson <pj@sgi.com>, linux-kernel@vger.kernel.org,
       frankeh@watson.ibm.com, haveblue@us.ibm.com
Subject: Re: [RFC] [PATCH 00/13] Introduce task_pid api
Message-ID: <20051115170819.GC2832@IBM-BWN8ZTBWAO1>
References: <20051114212341.724084000@sergelap> <20051114153649.75e265e7.pj@sgi.com> <20051115010155.GA3792@IBM-BWN8ZTBWAO1> <20051114175140.06c5493a.pj@sgi.com> <20051115022931.GB6343@sergelap.austin.ibm.com> <20051114193715.1dd80786.pj@sgi.com> <20051115051501.GA3252@IBM-BWN8ZTBWAO1> <20051115164708.GA12807@kroah.com>
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Quoting Greg KH (greg@kroah.com):
> On Mon, Nov 14, 2005 at 11:15:01PM -0600, Serge E. Hallyn wrote:
> > Quoting Paul Jackson (pj@sgi.com):
> > > Serge wrote:
> > > > the vserver model
> > > 
> > > What's that?
> > 
> > :)  Well a vserver pretends to be a full system of its own, though you
> > can have lots of vservers on one machine.  Processes in each virtual
> > server see only other processes in the same vserver.  However in
> > vserver the pids they see are the real kernel pids - except for one
> > process per vserver which can be the fakeinit.  Other processes in the
> > same vserver see it as pid 1, but to the kernel it is still known by
> > its real pid.
> 
> Why not just use Xen?  It can handle process migration from one virtual
> machine to another just fine.

It handles vm migration, but not process migration.  The most compelling
thing (imo) which the latter allows you to do is live OS upgrade under
an application.  Xen won't let you do that.  Of course load-balancing is
also more fine-grained and powerful with process set migration, and
the overhead of a full OS per migrateable job is quite heavy.

That's not to say we don't also want to use Xen :) - it has it's own
advantages and I'm not intending to denigrate those.  We just hope to
get both!

-serge

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