nvme: only use power of two io boundaries

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The kernel requires a power of two for boundaries because that's the
only way it can efficiently split commands that cross them. A
controller, however, may report a non-power of two boundary.

The driver had been rounding the controller's value to one the kernel
can use, but splitting on the wrong boundary provides no benefit on the
device side, and incurs additional submission overhead from non-optimal
splits.

Don't provide any boundary hint if the controller's value can't be used
and log a warning when first scanning a disk's unreported IO boundary.
Since the chunk sector logic has grown, move it to a separate function.

Cc: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>

...

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Keith Busch 2020-08-27 10:38:57 -07:00 • committed by Sagi Grimberg

parent 192f6c29bb

commit e83d776f9f

1 changed files with 38 additions and 9 deletions

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drivers/nvme/host/core.c

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