On Mon, Jan 30, 2017 at 12:06:19PM +0000, Safka, JaroslavX wrote:
-----Original Message----- From: Daniel P. Berrange [mailto:berrange@redhat.com] Sent: Monday, January 30, 2017 12:35 PM To: Michal Privoznik <mprivozn@redhat.com> Cc: Safka, JaroslavX <jaroslavx.safka@intel.com>; libvir-list@redhat.com; Mooney, Sean K <sean.k.mooney@intel.com>; Ptacek, MichalX <michalx.ptacek@intel.com> Subject: Re: [libvirt] [PATCHv4 0/3] Add support for file memorybacking
On 13.12.2016 13:12, Jaroslav Safka wrote:
Hi, we would like to introduce 3 new elements source,access and allocation in memoryBacking element. For now it was made for numa topology.
<memoryBacking> <source type="file|anonymous"/> <access mode="shared|private"/> <allocation mode="immediate|ondemand"/> </memoryBacking>
If allocation is immediate then -mem-prealloc should be added to the qemu commanline. If source is file then -object memory-backend-file,id=mem,size=1024M,mem-path=*lib dir path* -numa node,memdev=mem Will be added to the qemu commandline
If access is shared then the "share=on" parameter will be added to the memory-backend-file e.g. -object memory-backend-file,id=mem,size=1024M,mem-
On Sat, Jan 28, 2017 at 03:03:02PM +0100, Michal Privoznik wrote: path=/var/lib/libvirt/qemu
,share=on
The access mode can be overriden by specifying token memAccess in numa cell.
The test cpu-numa-memshared was removed, because behaviour was changed and is not needed anymore
I beg to disagree. What if you don't have any <memoryBacking/>?
I like these patches, but I'm not certainly sure about: a) domain XML (in the past we used to require an ACK on schema change from one of the Dans)
What are you unsure about ? This XML is what I suggested in previous rounds of discussion.
b) the location for qemu to create its mmaped files (patch 3/3). cfg->libDir looks very suspicious.
Well we've got two possibilities - source=anonymous, should be using /dev/shm, similar to how we do huge pages. For source=file, we need a real filesystem. Something under /var/lib/libvirt is reasonable. Perhaps a dedicated dir is needed ? eg /var/lib/libvirt/ram in order to provide a point where the admin can mount a sufficiently large filesystem ? Or make it configurable in /etc/libvirt/qemu.conf
[Jarek] It will be ok when I do something like libDir + "/ram". Or It should be configurable on compilation time?
Oh, I see that Dan already suggested to make it configurable. I would say both. Make it configurable in qemu.conf and use /var/lib/libvirt/ram as a default path. Pavel