Re: [PATCH v5 07/12] md: support to align bio to limits

On Mon, Jan 19, 2026 at 03:21:14PM +0800, Yu Kuai wrote:
> Hi，
> 
> 在 2026/1/19 14:47, Christoph Hellwig 写道:
> > On Sun, Jan 18, 2026 at 07:40:23PM +0800, Yu Kuai wrote:
> >> No, the chunk_sectors and io_opt are different, and align io to io_opt
> >> is not a general idea, for now this is the only requirement in mdraid.
> > The chunk size was added for (hardware) devices that require I/O split at
> > a fixed granularity for performance reasons.  Which seems to e exactly
> > what you want here.
> >
> > This has nothing to do with max_sectors.
> 
> For example, 32 disks raid5 array with chunksize=64k, currently the queue
> limits are:
> 
> chunk_sectors = 64k
> io_min = 64k
> io_opt = 64 * 31k
> max_sectors = 1M
> 
> It's correct to split I/O at 64k boundary to avoid performance issues, however
> split at 64 *31k boundary is what we want to get best bandwidth.
> 
> So, if we simply changes chunk_sectors to 64 * 31k, it will be incorrect, because
> 64k boundary is still necessary for small IO.

What do you mean with "necessary for small IO"?