> On Jun 17, 2022, at 7:54 PM, Klaus Jensen <i...@irrelevant.dk> wrote:
>
> On Jun 16 20:34, Jinhao Fan wrote:
>> This patch adds shadow doorbell buffer support in NVMe 1.3 to QEMU
>> NVMe. The Doorbell Buffer Config admin command is implemented for the
>> guest to enable shadow doobell buffer. When this feature is enabled, each
>> SQ/CQ is associated with two buffers, i.e., Shadow Doorbell buffer and
>> EventIdx buffer. According to the Spec, each queue's doorbell register
>> is only updated when the Shadow Doorbell buffer value changes from being
>> less than or equal to the value of the corresponding EventIdx buffer
>> entry to being greater than that value. Therefore, the number of MMIO's
>> on the doorbell registers is greatly reduced.
>>
>> This patch is adapted from Huaicheng Li's patch[1] in 2018.
>>
>> [1]
>> https://patchwork.kernel.org/project/qemu-devel/patch/20180305194906.ga3...@gmail.com/
>>
>> IOPS comparison with FIO:
>>
>> iodepth 1 2 4 8
>> QEMU 25.1k 25.9k 24.5k 24.0k
>> +dbbuf 29.1k 60.1k 99.8k 82.5k
>>
>> MMIO's per IO measured by perf-kvm:
>>
>> iodepth 1 2 4 8
>> QEMU 2.01 1.99 1.99 1.99
>> +dbbuf 1.00 0.52 0.27 0.46
>>
>> The tests are done on Ubuntu 22.04 with 5.15.0-33 kernel with Intel(R)
>> Xeon(R) Gold 6248R CPU @ 3.00GHz.
>>
>> QEMU set up:
>>
>> bin/x86_64-softmmu/qemu-system-x86_64 \
>> -name "nvme-test" \
>> -machine accel=kvm \
>> -cpu host \
>> -smp 4 \
>> -m 8G \
>> -daemonize \
>> -device virtio-scsi-pci,id=scsi0 \
>> -device scsi-hd,drive=hd0 \
>> -drive
>> file=$OSIMGF,if=none,aio=native,cache=none,format=qcow2,id=hd0,snapshot=on \
>> -drive "id=nvm,if=none,file=null-co://,file.read-zeroes=on,format=raw" \
>> -device nvme,serial=deadbeef,drive=nvm \
>> -net user,hostfwd=tcp::8080-:22 \
>> -net nic,model=virtio
>>
>> FIO configuration:
>>
>> [global]
>> ioengine=libaio
>> filename=/dev/nvme0n1
>> thread=1
>> group_reporting=1
>> direct=1
>> verify=0
>> time_based=1
>> ramp_time=0
>> runtime=30
>> ;size=1G
>> ;iodepth=1
>> rw=randread
>> bs=4k
>>
>> [test]
>> numjobs=1
>>
>> Changes since v2:
>> - Do not ignore admin queue updates in nvme_process_db and nvme_post_cqes
>> - Calculate db_addr and ei_addr in hard-coded way
>>
>> Changes since v1:
>> - Add compatibility with hosts that do not use admin queue shadow doorbell
>>
>> Jinhao Fan (2):
>> hw/nvme: Implement shadow doorbell buffer support
>> hw/nvme: Add trace events for shadow doorbell buffer
>>
>> hw/nvme/ctrl.c | 118 ++++++++++++++++++++++++++++++++++++++++++-
>> hw/nvme/nvme.h | 8 +++
>> hw/nvme/trace-events | 5 ++
>> include/block/nvme.h | 2 +
>> 4 files changed, 132 insertions(+), 1 deletion(-)
>>
>> --
>> 2.25.1
>>
>
> LGTM,
>
> Reviewed-by: Klaus Jensen <k.jen...@samsung.com>
>
Great!
I have two questions:
How many “Reviewed-by”’s do I need to get my patch applied?
Do I need to post a v4 patch to add the “Reviewed-by”’s in my commit
message?
Thanks,
Jinhao Fan
