Re: [PATCH] xfs: update BDI {io,ra}_pages values based on the RT device limits

[Damien Le Moal <dlemoal@kernel.org>]

On 6/23/26 23:21, Christoph Hellwig wrote:
> When using XFS with a main device on an SSD that stores metadata and a RT
> device to store data on a HDD, we fail to take the I/O sizes for the RT
> device into accounting, leading to up to 5% slower read performance when
> using an SSD for metadata vs storing data and metadata on the HDD.
> 
> Fix this up by taking the RT settings into account.  Note that this
> updates the BDI owned by the main device, and leaves those settings in
> place even when the file system is unmounted.  This is a bit unexpected
> but not different from manual tuning through sysfs (although that is only
> possible for the ra_pages value).
> 
> Reported-by: Filip Blagojevic <filip.blagojevic@wdc.com>
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Until we have a better API to do this, given the performance improvements this
gives with HDDs, I am all for it.

Reviewed-by: Damien Le Moal <dlemoal@kernel.org>

-- 
Damien Le Moal
Western Digital Research