Re: [PATCH v8 5/5] multifd: Implement zero copy write in multifd migration (multifd-zero-copy)

[Peter Xu]

On Tue, Feb 01, 2022 at 03:29:03AM -0300, Leonardo Bras wrote:
> -void multifd_send_sync_main(QEMUFile *f)
> +int multifd_send_sync_main(QEMUFile *f)
>  {
>      int i;
> +    bool flush_zero_copy;
>  
>      if (!migrate_use_multifd()) {
> -        return;
> +        return 0;
>      }
>      if (multifd_send_state->pages->num) {
>          if (multifd_send_pages(f) < 0) {
>              error_report("%s: multifd_send_pages fail", __func__);
> -            return;
> +            return 0;

I've not checked how it used to do if multifd_send_pages() failed, but.. should
it returns -1 rather than 0 when there will be a return code?

>          }
>      }
> +
> +    /*
> +     * When using zero-copy, it's necessary to flush after each iteration to
> +     * make sure pages from earlier iterations don't end up replacing newer
> +     * pages.
> +     */
> +    flush_zero_copy = migrate_use_zero_copy_send();
> +
>      for (i = 0; i < migrate_multifd_channels(); i++) {
>          MultiFDSendParams *p = &multifd_send_state->params[i];
>  
> @@ -591,7 +600,7 @@ void multifd_send_sync_main(QEMUFile *f)
>          if (p->quit) {
>              error_report("%s: channel %d has already quit", __func__, i);
>              qemu_mutex_unlock(&p->mutex);
> -            return;
> +            return 0;

Same question here.

>          }

The rest looks good.  Thanks,

-- 
Peter Xu