On Thu, 3 Mar 2016 18:44:28 +0800
Liang Li <liang.z.li@xxxxxxxxx> wrote:
> Get the free pages information through virtio and filter out the free
> pages in the ram bulk stage. This can significantly reduce the total
> live migration time as well as network traffic.
>
> Signed-off-by: Liang Li <liang.z.li@xxxxxxxxx>
> ---
> migration/ram.c | 52 ++++++++++++++++++++++++++++++++++++++++++++++------
> 1 file changed, 46 insertions(+), 6 deletions(-)
>
> @@ -1945,6 +1971,20 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
> DIRTY_MEMORY_MIGRATION);
> }
> memory_global_dirty_log_start();
> +
> + if (balloon_free_pages_support() &&
> + balloon_get_free_pages(migration_bitmap_rcu->free_pages_bmap,
> + &free_pages_count) == 0) {
> + qemu_mutex_unlock_iothread();
> + while (balloon_get_free_pages(migration_bitmap_rcu->free_pages_bmap,
> + &free_pages_count) == 0) {
> + usleep(1000);
> + }
> + qemu_mutex_lock_iothread();
> +
> + filter_out_guest_free_pages(migration_bitmap_rcu->free_pages_bmap);
A general comment: Using the ballooner to get information about pages
that can be filtered out is too limited (there may be other ways to do
this; we might be able to use cmma on s390, for example), and I don't
like hardcoding to a specific method.
What about the reverse approach: Code may register a handler that
populates the free_pages_bitmap which is called during this stage?
<I like the idea of filtering in general, but I haven't looked at the
code yet>
> + }
> +
> migration_bitmap_sync();
> qemu_mutex_unlock_ramlist();
> qemu_mutex_unlock_iothread();
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