* Andrey Gruzdev (andrey.gruz...@virtuozzo.com) wrote:
> Introducing implementation of 'background' snapshot thread
> which in overall follows the logic of precopy migration
> while internally utilizes completely different mechanism
> to 'freeze' vmstate at the start of snapshot creation.
>
> This mechanism is based on userfault_fd with wr-protection
> support and is Linux-specific.
I noticed there weren't any bdrv_ calls in here; I guess with a snapshot
you still have the source running so still have it accessing the disk;
do you do anything to try and wire the ram snapshotting up to disk
snapshotting?
> Signed-off-by: Andrey Gruzdev <andrey.gruz...@virtuozzo.com>
> Acked-by: Peter Xu <pet...@redhat.com>
> ---
> migration/migration.c | 255 +++++++++++++++++++++++++++++++++++++++++-
> migration/migration.h | 3 +
> migration/ram.c | 2 +
> migration/savevm.c | 1 -
> migration/savevm.h | 2 +
> 5 files changed, 260 insertions(+), 3 deletions(-)
>
> diff --git a/migration/migration.c b/migration/migration.c
> index 2c2cb9ef01..0901a15ac5 100644
<snip>
> - qemu_thread_create(&s->thread, "live_migration", migration_thread, s,
> - QEMU_THREAD_JOINABLE);
> +
> + if (migrate_background_snapshot()) {
> + qemu_thread_create(&s->thread, "background_snapshot",
Unfortunately that wont work - there's a 14 character limit on
the thread name length; I guess we just shorten that to bg_snapshot
Other than that,
Reviewed-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
> + bg_migration_thread, s, QEMU_THREAD_JOINABLE);
> + } else {
> + qemu_thread_create(&s->thread, "live_migration",
> + migration_thread, s, QEMU_THREAD_JOINABLE);
> + }
> s->migration_thread_running = true;
> }
>
> diff --git a/migration/migration.h b/migration/migration.h
> index f40338cfbf..0723955cd7 100644
> --- a/migration/migration.h
> +++ b/migration/migration.h
> @@ -20,6 +20,7 @@
> #include "qemu/thread.h"
> #include "qemu/coroutine_int.h"
> #include "io/channel.h"
> +#include "io/channel-buffer.h"
> #include "net/announce.h"
> #include "qom/object.h"
>
> @@ -147,8 +148,10 @@ struct MigrationState {
>
> /*< public >*/
> QemuThread thread;
> + QEMUBH *vm_start_bh;
> QEMUBH *cleanup_bh;
> QEMUFile *to_dst_file;
> + QIOChannelBuffer *bioc;
> /*
> * Protects to_dst_file pointer. We need to make sure we won't
> * yield or hang during the critical section, since this lock will
> diff --git a/migration/ram.c b/migration/ram.c
> index 5707382db1..05fe0c8592 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -1471,6 +1471,7 @@ static RAMBlock *poll_fault_page(RAMState *rs,
> ram_addr_t *offset)
> page_address = (void *) uffd_msg.arg.pagefault.address;
> bs = qemu_ram_block_from_host(page_address, false, offset);
> assert(bs && (bs->flags & RAM_UF_WRITEPROTECT) != 0);
> +
> return bs;
> }
> #endif /* CONFIG_LINUX */
> @@ -1836,6 +1837,7 @@ static void ram_save_host_page_post(RAMState *rs,
> PageSearchStatus *pss,
> /* Un-protect memory range. */
> res = uffd_change_protection(rs->uffdio_fd, page_address, run_length,
> false, false);
> +
> /* We don't want to override existing error from
> ram_save_host_page(). */
> if (res < 0 && *res_override >= 0) {
> *res_override = res;
> diff --git a/migration/savevm.c b/migration/savevm.c
> index 27e842812e..dd4ad0aaaf 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -1354,7 +1354,6 @@ int
> qemu_savevm_state_complete_precopy_iterable(QEMUFile *f, bool in_postcopy)
> return 0;
> }
>
> -static
> int qemu_savevm_state_complete_precopy_non_iterable(QEMUFile *f,
> bool in_postcopy,
> bool inactivate_disks)
> diff --git a/migration/savevm.h b/migration/savevm.h
> index ba64a7e271..aaee2528ed 100644
> --- a/migration/savevm.h
> +++ b/migration/savevm.h
> @@ -64,5 +64,7 @@ int qemu_loadvm_state(QEMUFile *f);
> void qemu_loadvm_state_cleanup(void);
> int qemu_loadvm_state_main(QEMUFile *f, MigrationIncomingState *mis);
> int qemu_load_device_state(QEMUFile *f);
> +int qemu_savevm_state_complete_precopy_non_iterable(QEMUFile *f,
> + bool in_postcopy, bool inactivate_disks);
>
> #endif
> --
> 2.25.1
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
