[ovirt-devel] VDSM faqemu default memory change

Dan Kenigsberg danken at redhat.com
Tue Jun 24 10:17:37 UTC 2014

On Tue, Jun 17, 2014 at 11:09:26PM +0100, Dan Kenigsberg wrote:
> On Tue, Jun 10, 2014 at 10:43:36AM -0400, Martin Polednik wrote:
> > Hello
> > 
> > I'm writing in order to propose a change to faqemu hook as indicated in [1],
> > modifying the hook's default behavior:
> > 
> > There are currently hardcoded x86_64 and PPC memory limits (20480 and 262144),
> > this change would remove these implicit constraints and keep the memory unchanged.
> > A new variable in configuration is introduced, fake_kvm_memory, which allows you
> > to limit the memory for both these platforms to a value (or using unchanged memory
> > by setting it to 0, which is default).
> > 
> > This means that running faqemu without modification would consume up to 10x times
> > memory using default VM memory memory size for x86_64 and unchanged for PPC.
> > 
> > [1] http://gerrit.ovirt.org/#/c/28320/
> Let me rephrase the warning: Now, faqemu runs a qemu with the tiniest
> memory possible, that is unable to host any guest. This makes it
> maintain its purpose of seeming like a VM yet taking the least amounts
> possible of CPU and memory.
> With the suggested patch, this changes. Unless explicitly setting
> fake_kvm_memory=20480, each qemu process would consume the full amount
> of memory allocated to it. Anybody using faqemu should be aware of the
> proposed change and agree to it.
> If the users are unhappy with this, I'd suggest Martin to have a fresh
> and simpler new hook, that only change the domain type from "kvm" to
> "qemu", with no configurables and no change of behavior. On a second
> thought, I belive it would be better, as with a fully-operational
> emulated guest, this is no loger a fake qemu, but just a slow one.

Friendly reminder: if no objections are expressed in this venue, faqemu
default momeory size would change!


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