Increase maxsize of io_queue_depth for nvme driver?

[Keith Busch]

On Sun, Sep 14, 2025 at 02:45:35PM +0200, Apachez wrote:
> I would like to propose that NVME_PCI_MAX_QUEUE_SIZE should be
> increased from 4095 to 32767 to match the current NVMe specification
> regarding MQES and to give the sysop ability to fully utilize the
> performance of the hardware being used, or am I missing something
> here?

We use the upper bits of the command id to detect duplicate completions,
so we don't have enough bits to tag commands beyond 4095. As far as I
know, though, we haven't seen such breakage in a *long* time. It's more
of a sanity thing to know with high certainty that duplicate completions
are not occurring.

But I don't think you'll see any performance difference by increasing
the queue depth. Devices saturate the link at far lower already, so
going higher just increases completion latency.