On Thu, Jan 21, 2016 at 08:15:37PM -0800, Linus Torvalds wrote:
For the case of nvme, for example, I think the max sector number is so
high that you'll never hit that anyway, and you'll only ever hit the
chunk limit. No?
The device's max transfer and chunk size are not very large, both fixed
at 128KB. We can lose ~70% of potential throughput when IO isn't aligned,
and end users reported this when the block layer stopped splitting on
alignment for the NVMe drive.
So it's a big deal for this h/w, but now I feel awkward defending a
device specific feature for the generic block layer.
Anyway, the patch was developed with incorrect assumptions. I'd still
like to try again after reconciling the queue limit constraints, but
I defer to Jens for the near term.