Re: [Qemu-devel] [PATCH v2] migration/block: Avoid invoking blk_drain too frequently

[Fam Zheng <famz@redhat.com>]

On Wed, 03/15 11:37, Lidong Chen wrote:
> Increase bmds->cur_dirty after submit io, so reduce the frequency
> involve into blk_drain, and improve the performance obviously
> when block migration.
> 
> The performance test result of this patch:
> 
> During the block dirty save phase, this patch improve guest os IOPS
> from 4.0K to 9.5K. and improve the migration speed from
> 505856 rsec/s to 855756 rsec/s.
> 
> Signed-off-by: Lidong Chen <jemmy858585@gmail.com>
> ---
>  migration/block.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/migration/block.c b/migration/block.c
> index 6741228..7734ff7 100644
> --- a/migration/block.c
> +++ b/migration/block.c
> @@ -576,6 +576,9 @@ static int mig_save_device_dirty(QEMUFile *f, BlkMigDevState *bmds,
>              }
>  
>              bdrv_reset_dirty_bitmap(bmds->dirty_bitmap, sector, nr_sectors);
> +            sector += nr_sectors;
> +            bmds->cur_dirty = sector;
> +
>              break;
>          }
>          sector += BDRV_SECTORS_PER_DIRTY_CHUNK;
> -- 
> 1.8.3.1
> 

Nice catch above all, thank you!

Reviewed-by: Fam Zheng <famz@redhat.com>