* Peter Xu (pet...@redhat.com) wrote:
> Firstly, renaming the old matching_page_sizes variable to
> matching_target_page_size, which suites more to what it did (it only
> checks against target page size rather than multiple page sizes).
> Meanwhile, simplify the check logic a bit, and enhance the comments.
> Should have no functional change.
>
> Signed-off-by: Peter Xu <pet...@redhat.com>
> ---
> migration/ram.c | 17 +++++++++++------
> 1 file changed, 11 insertions(+), 6 deletions(-)
>
> diff --git a/migration/ram.c b/migration/ram.c
> index 23cea47090..fbeb23f750 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -3580,7 +3580,7 @@ static int ram_load_postcopy(QEMUFile *f)
> {
> int flags = 0, ret = 0;
> bool place_needed = false;
> - bool matching_page_sizes = false;
> + bool matching_target_page_size = false;
> MigrationIncomingState *mis = migration_incoming_get_current();
> /* Temporary page that is later 'placed' */
> void *postcopy_host_page = postcopy_get_tmp_page(mis);
> @@ -3620,7 +3620,7 @@ static int ram_load_postcopy(QEMUFile *f)
> ret = -EINVAL;
> break;
> }
> - matching_page_sizes = block->page_size == TARGET_PAGE_SIZE;
> + matching_target_page_size = block->page_size == TARGET_PAGE_SIZE;
That's OK, although 'matches_target_page_size' would be better wording.
('matching_target_page_size' implies we know something about the sources
target page size)
> /*
> * Postcopy requires that we place whole host pages atomically;
> * these may be huge pages for RAMBlocks that are backed by
> @@ -3668,12 +3668,17 @@ static int ram_load_postcopy(QEMUFile *f)
>
> case RAM_SAVE_FLAG_PAGE:
> all_zero = false;
> - if (!place_needed || !matching_page_sizes) {
> + if (!matching_target_page_size) {
> + /* For huge pages, we always use temporary buffer */
> qemu_get_buffer(f, page_buffer, TARGET_PAGE_SIZE);
> } else {
> - /* Avoids the qemu_file copy during postcopy, which is
> - * going to do a copy later; can only do it when we
> - * do this read in one go (matching page sizes)
> + /*
> + * For small pages that matches target page size, we
> + * avoid the qemu_file copy. Instead we directly use
> + * the buffer of QEMUFile to place the page. Note: we
> + * cannot do any QEMUFile operation before using that
> + * buffer to make sure the buffer is valid when
> + * placing the page.
> */
> qemu_get_buffer_in_place(f, (uint8_t **)&place_source,
> TARGET_PAGE_SIZE);
But, yes I think that's right; since this is in ram_load_postcopy
the only time we have !place_needed is in the not-last subpage of a
hugepage (or host page > target_page), so that's already covered
by the !matching_page_sizes check.
Reviewed-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
> --
> 2.17.1
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
