Re: [Qemu-block] [Qemu-devel] [PATCH] migration/block: Avoid involve into blk_drain too frequently

[Eric Blake]

On 03/14/2017 02:57 AM, address@hidden wrote:
> From: Lidong Chen <address@hidden>
> 
> Increase bmds->cur_dirty after submit io, so reduce the frequency involve 
> into blk_drain, and improve the performance obviously when block migration.

Long line; please wrap your commit messages, preferably around 70 bytes
since 'git log' displays them indented, and it is still nice to read
them in an 80-column window.

Do you have benchmark numbers to prove the impact of this patch, or even
a formula for reproducing the benchmark testing?

> 
> Signed-off-by: Lidong Chen <address@hidden>
> ---
>  migration/block.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/migration/block.c b/migration/block.c
> index 6741228..f059cca 100644
> --- a/migration/block.c
> +++ b/migration/block.c
> @@ -576,6 +576,8 @@ 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;
> 

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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