While looking at VM bootup times, we stumbled over the fact that the NVMe code only does I/O operations of up to 4kb at a given point in time. This is usually ok, but if you have an OS that loads a lot of data on boot in combination to network backed storage, it shows in bootup times.
There is no need to restrict ourselves to 4kb though. The INT13 call we receive gives us much larger chunks which we can just map into a native bigger NVMe I/O call if the request buffer is page aligned.
This patch implements all logic required to do the above and gives a substantial performance boost on boot.
v1 -> v2:
- fix dprintf - Fix bounds check on PRP list add logic - Reduce PRP list to 15 entries embedded in the ns struct. This reduces BIOS reserved memory footprint by 4kb.
v2 -> v3:
- new patch: nvme: Split requests by maximum allowed size - Adjust the maximum request size to sector units. The hardware field describes it in pages.
Alexander Graf (4): nvme: Record maximum allowed request size nvme: Allow to set PRP2 nvme: Pass large I/O requests as PRP lists nvme: Split requests by maximum allowed size
src/hw/nvme-int.h | 16 ++++++- src/hw/nvme.c | 122 +++++++++++++++++++++++++++++++++++++++++++++++------- 2 files changed, 121 insertions(+), 17 deletions(-)