"Dr. David Alan Gilbert (git)" <dgilb...@redhat.com> wrote: > From: "Dr. David Alan Gilbert" <dgilb...@redhat.com> > > Signed-off-by: Dr. David Alan Gilbert <dgilb...@redhat.com> > --- > docs/migration.txt | 13 +++++++++++++ > 1 file changed, 13 insertions(+) > > diff --git a/docs/migration.txt b/docs/migration.txt > index 6503c17..b462ead 100644 > --- a/docs/migration.txt > +++ b/docs/migration.txt > @@ -482,3 +482,16 @@ request for a page that has already been sent is > ignored. Duplicate requests > such as this can happen as a page is sent at about the same time the > destination accesses it. > > +=== Postcopy with hugepages === > + > +Postcopy now works with hugetlbfs backed memory: > + a) The linux kernel on the destination must support userfault on hugepages. > + b) The huge-page configuration on the source and destination VMs must be > + identical; i.e. RAMBlocks on both sides must use the same page size. > + c) Note that -mem-path /dev/hugepages will fall back to allocating normal > + RAM if it doesn't have enough hugepages, triggering (b) to fail. > + Using -mem-prealloc enforces the allocation using hugepages. > + d) Care should be taken with the size of hugepage used; postcopy with 2MB > + hugepages works well, however 1GB hugepages are likely to be problematic > + since it takes ~1 second to transfer a 1GB hugepage across a 10Gbps > link, > + and until the full page is transferred the destination thread is > blocked.
Reviewed-by: Juan Quintela <quint...@redhat.com>
