Re: [PATCH v2 08/11] md/raid5: align bio to io_opt

在 2026/1/3 23:45, Yu Kuai 写道:
> raid5 internal implementaion indicates that if write bio is aligned to
> io_opt, then full stripe write will be used, which will be best for
> bandwidth because there is no need to read extra data to build new
> xor data.
> 
> Simple test in my VM, 32 disks raid5 with 64kb chunksize:
> dd if=/dev/zero of=/dev/md0 bs=100M oflag=direct
> 
> Before this patch:  782 MB/s
> With this patch:    1.1 GB/s
> 
> BTW, there are still other bottleneck related to stripe handler, and
> require further optimization.
> 
> Signed-off-by: Yu Kuai <[email protected]>
> ---
>   drivers/md/raid5.c | 6 ++----
>   1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
> index 005a2404de27..69a5eb02b891 100644
> --- a/drivers/md/raid5.c
> +++ b/drivers/md/raid5.c
> @@ -59,8 +59,7 @@
>   #define UNSUPPORTED_MDDEV_FLAGS		\
>   	((1L << MD_FAILFAST_SUPPORTED) |	\
>   	 (1L << MD_FAILLAST_DEV) |		\
> -	 (1L << MD_SERIALIZE_POLICY) |		\
> -	 (1L << MD_BIO_ALIGN))
> +	 (1L << MD_SERIALIZE_POLICY))
>   
>   
>   #define cpu_to_group(cpu) cpu_to_node(cpu)
> @@ -7818,8 +7817,7 @@ static int raid5_set_limits(struct mddev *mddev)
>   	 * Limit the max sectors based on this.
>   	 */
>   	lim.max_hw_sectors = RAID5_MAX_REQ_STRIPES << RAID5_STRIPE_SHIFT(conf);
> -	if ((lim.max_hw_sectors << 9) < lim.io_opt)
> -		lim.max_hw_sectors = lim.io_opt >> 9;
> +	md_config_align_limits(mddev, &lim);
>   
>   	/* No restrictions on the number of segments in the request */
>   	lim.max_segments = USHRT_MAX;

LGTM

Reviewed-by: Li Nan <[email protected]>
-- 
Thanks,
Nan