Re: [PATCH v6 00/15] RAM_NORESERVE, MAP_NORESERVE and hostmem "reserve" property

[David Hildenbrand]

On 21.04.21 23:06, Eduardo Habkost wrote:
> On Wed, Apr 21, 2021 at 02:26:09PM +0200, David Hildenbrand wrote:
> > Based-on: 20210406080126.24010-1-david@redhat.com
> >
> > Some cleanups previously sent in other context (resizeable allocations),
> > followed by RAM_NORESERVE, implementing it under Linux using MAP_NORESERVE,
> > and letting users configure it for memory backens using the "reserve"
> > property (default: true).
> >
> > MAP_NORESERVE under Linux has in the context of QEMU an effect on
> > 1) Private/shared anonymous memory
> > -> memory-backend-ram,id=mem0,size=10G
> > 2) Private fd-based mappings
> > -> memory-backend-file,id=mem0,size=10G,mem-path=/dev/shm/0
> > -> memory-backend-memfd,id=mem0,size=10G
> > 3) Private/shared hugetlb mappings
> > -> memory-backend-memfd,id=mem0,size=10G,hugetlb=on,hugetlbsize=2M
> >
> > With MAP_NORESERVE/"reserve=off", we won't be reserving swap space (1/2) or
> > huge pages (3) for the whole memory region.
> >
> > The target use case is virtio-mem, which dynamically exposes memory
> > inside a large, sparse memory area to the VM. MAP_NORESERVE tells the OS
> > "this mapping might be very sparse". This essentially allows
> > avoiding having to set "/proc/sys/vm/overcommit_memory == 1") when using
> > virtio-mem and also supporting hugetlbfs in the future.
>
> For the memory backend and machine core code:
>
> Acked-by: Eduardo Habkost <ehabkost@redhat.com>

Thanks Eduardo. I assume Paolo will be the right maintainer to pick this 
up? (I hope he'll have time to look at this and some of my 
pending-for-a-long-time series soon :( )

--
Thanks,

David / dhildenb