"Dr. David Alan Gilbert (git)" <dgilb...@redhat.com> wrote:
> From: "Dr. David Alan Gilbert" <dgilb...@redhat.com>
>
> Where postcopy is preceeded by a period of precopy, the destination will
> have received pages that may have been dirtied on the source after the
> page was sent. The destination must throw these pages away before
> starting it's CPUs.
>
> Maintain a 'sentmap' of pages that have already been sent.
> Calculate list of sent & dirty pages
> Provide helpers on the destination side to discard these.
>
> Signed-off-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
Not a patch without a suggestion O:-)
> ---
> include/migration/migration.h | 12 +++
> include/migration/postcopy-ram.h | 35 +++++++
> include/qemu/typedefs.h | 1 +
> migration/migration.c | 1 +
> migration/postcopy-ram.c | 108 +++++++++++++++++++++
> migration/ram.c | 203
> ++++++++++++++++++++++++++++++++++++++-
> migration/savevm.c | 2 -
> trace-events | 5 +
> 8 files changed, 363 insertions(+), 4 deletions(-)
>
> diff --git a/include/migration/migration.h b/include/migration/migration.h
> index 2a22381..4c6cf95 100644
> --- a/include/migration/migration.h
> +++ b/include/migration/migration.h
> @@ -114,6 +114,13 @@ struct MigrationState
>
> /* Flag set once the migration has been asked to enter postcopy */
> bool start_postcopy;
> +
> + /* bitmap of pages that have been sent at least once
> + * only maintained and used in postcopy at the moment
> + * where it's used to send the dirtymap at the start
> + * of the postcopy phase
> + */
> + unsigned long *sentmap;
> };
We can use this sentmap for zero page optimization. If page is on
sentmap, we need to sent a zero page, otherwise, just sent sentmap at
the end of migration and clean everything not there?
> +/*
> + * Discard the contents of memory start..end inclusive.
> + * We can assume that if we've been called postcopy_ram_hosttest returned
> true
> + */
> +int postcopy_ram_discard_range(MigrationIncomingState *mis, uint8_t *start,
> + uint8_t *end)
> +{
> + trace_postcopy_ram_discard_range(start, end);
> + if (madvise(start, (end-start)+1, MADV_DONTNEED)) {
Can we s/end/lenght/ and adjust everywhere?
Not here, but putting a comment explaining where magic 12 cames from on
definition of constant?
I think that the sentbitmap bits could we used without the rest.
