On 06/02/2017 18:33, Dr. David Alan Gilbert (git) 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: Laurent Vivier <lviv...@redhat.com>
