[libvirt] PING: [RFC] vhost-user + shared memory + NUMA
Hello! Sorry, but i did not get any answer to the last question. Would it be OK to require <memoryBacking> and implicitly add only shared mode ? Kind regards, Pavel Fedin Senior Engineer Samsung Electronics Research center Russia
-----Original Message----- From: libvir-list-bounces@redhat.com [mailto:libvir-list-bounces@redhat.com] On Behalf Of Pavel Fedin Sent: Thursday, February 11, 2016 5:36 PM To: 'Daniel P. Berrange' Cc: 'Libvirt' Subject: Re: [libvirt] [RFC] vhost-user + shared memory + NUMA
Hello!
Ok, then would it be a good compromise if we require <memoryBacking>, and only implicitly add "shared" if we have vhost-user devices? This way we would not change the way the guest memory is allocated.
Adding shared implicitly *will* change the way guest memory is allocated, as it will have to use tmpfs to make it shared.
You perhaps didn't get my idea. I meant - we will still need to specify <memoryBacking> with huge pages, just no <numa>. Therefore, the memory will be allocated via file backend from hugetlbfs. Only mode will be changed implicitly (private -> shared).
IMHO being able to manually specify "shared" both in <numa> and in <memoryBacking> would be ambiguous.
That's not really any different to what we have already with NUMA. The top level setting would apply as the default, and the NUMA level settings override it if needed.
Well, the only little drawback would be necessity to add "shared" by itself. This would require additional patching to clients (e. g. openstack).
Kind regards, Pavel Fedin Senior Engineer Samsung Electronics Research center Russia
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On Mon, Feb 15, 2016 at 04:38:51PM +0300, Pavel Fedin wrote:
Hello! Sorry, but i did not get any answer to the last question. Would it be OK to require <memoryBacking> and implicitly add only shared mode ?
No, I really think setting shared must be an explicit action by the app configuring libvirt. Automatically setting attributes based on other settings has come back to bite us too many times in the past. So I don't see any compelling reason to automatically set shared mode when using vhost-user. The low level XML config is *not* trying to be user friendly - its a low level interface. User friendly is for the application layer to care about. Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|
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Pavel Fedin