On Fri, Apr 23, 2021 at 12:35:35PM +0200, David Hildenbrand wrote: > 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-da...@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 <ehabk...@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 :( )
I can pick it up (or you could merge it through your tree if you prefer), but I would like to get at least an Acked-by from Paolo first. On the other hand, maybe v7 is mature enough to not require waiting too much longer. -- Eduardo
