Great! Thanks for the information. I'll be sure to mention it to our "Linux administrator" who is from the distributed side and has little or no mainframe experience.
-- John McKown Senior Technical Specialist UICI Insurance Center Applications & Solutions Team +1.817.255.3225 > -----Original Message----- > From: Rob van der Heij [mailto:[EMAIL PROTECTED]] > Sent: Friday, December 13, 2002 1:45 PM > To: [EMAIL PROTECTED] > Subject: Re: Linux/390 and z/VM interactions. > > > At 15:42 13-12-02, McKown, John wrote: > > >I know that I should "use the code, Luke", but I'm not that > familiar with > >the kernel et al. Does Linux/390 take advantage of any of > the VM facilities > >when running under VM vs. in an LPAR? I'm thinking especially of the > >"handshaking" that is possible with paging. I.e. Linux > thinks the page is in > >memory, but VM has it paged out. I think this is done with VSE and I > >remember it back in the OS/VS1 days as well. What about other VM-only > >facilities? > > Yes, pseudo page fault support is there already. When a > process gets blocked because the particular page is paged out > by VM, the kernel gets a chance to run another process. > Recent changes to z/VM improved the PFAULT support. I have > not seen numbers about how effective this is for Linux, but > it is enabled by default when you run in a virtual machine. > In fact, virtual memory itself as provided by z/VM is already > a benefit over LPAR since it allows the Linux guests to breathe. > > The other thing is the shared kernel support that has been > there for some time now. This allows you to put some 2MB of > the kernel in shared pages and thus reduce the footprint of > your penguins. > > And the dasd driver can use Diagnose I/O instead of SSCH and > exploit MDC and other z/VM benefits. There have been some > problems with that part of the driver in the past, but it > looks like the current code works. > > Rob >
