Re: [PATCH] xfs: always allocate the free zone with the lowest index

[Christoph Hellwig <hch@lst.de>]

On Tue, Jan 20, 2026 at 09:57:46AM +0100, Hans Holmberg wrote:
> Zones in the beginning of the address space are typically mapped to
> higer bandwidth tracks on HDDs than those at the end of the address
> space. So, in stead of allocating zones "round robin" across the whole
> address space, always allocate the zone with the lowest index.
> 
> This increases average write bandwidth for overwrite workloads
> when less than the full capacity is being used. At ~50% utilization
> this improves bandwidth for a random file overwrite benchmark
> with 128MiB files and 256MiB zone capacity by 30%.
> 
> Running the same benchmark with small 2-8 MiB files at 67% capacity
> shows no significant difference in performance. Due to heavy
> fragmentation the whole zone range is in use, greatly limiting the 
> number of free zones with high bw.

Cool, thanks!

Reviewed-by: Christoph Hellwig <hch@lst.de>

I always like patches that speed things up by removing code :)