Re: [PATCH 1/3] migration: Fix missing qemu_fflush() on buffer file in bg_migration_thread

[David Hildenbrand]

On 18.03.21 18:46, Andrey Gruzdev wrote:
> Added missing qemu_fflush() on buffer file holding precopy device state.
> Increased initial QIOChannelBuffer allocation to 512KB to avoid reallocs.
> Typical configurations often require >200KB for device state and VMDESC.
>
> Signed-off-by: Andrey Gruzdev <andrey.gruzdev@virtuozzo.com>
> ---
>   migration/migration.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/migration/migration.c b/migration/migration.c
> index 36768391b6..496cf6e17b 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -3857,7 +3857,7 @@ static void *bg_migration_thread(void *opaque)
>        * with vCPUs running and, finally, write stashed non-RAM part of
>        * the vmstate from the buffer to the migration stream.
>        */
> -    s->bioc = qio_channel_buffer_new(128 * 1024);
> +    s->bioc = qio_channel_buffer_new(512 * 1024);

^ would that better be a separate patch? It sounds more like an 
improvement than a fix.

>       qio_channel_set_name(QIO_CHANNEL(s->bioc), "vmstate-buffer");
>       fb = qemu_fopen_channel_output(QIO_CHANNEL(s->bioc));
>       object_unref(OBJECT(s->bioc));
> @@ -3911,6 +3911,8 @@ static void *bg_migration_thread(void *opaque)
>       if (qemu_savevm_state_complete_precopy_non_iterable(fb, false, false)) {
>           goto fail;
>       }
> +    qemu_fflush(fb);

Fixes: ?

> +
>       /* Now initialize UFFD context and start tracking RAM writes */
>       if (ram_write_tracking_start()) {
>           goto fail;


--
Thanks,

David / dhildenb