[bug report] iommu_dma_unmap_sg() is very slow then running IO from remote numa node

[John Garry]

On 21/07/2021 10:59, Ming Lei wrote:
>> I have now removed that from the tree, so please re-pull.
> Now the kernel can be built successfully, but not see obvious improvement
> on the reported issue:
> 
> [root at ampere-mtjade-04 ~]# uname -a
> Linux ampere-mtjade-04.khw4.lab.eng.bos.redhat.com 5.14.0-rc2_smmu_fix+ #2 SMP Wed Jul 21 05:49:03 EDT 2021 aarch64 aarch64 aarch64 GNU/Linux
> 
> [root at ampere-mtjade-04 ~]# taskset -c 0 ~/git/tools/test/nvme/io_uring 10 1 /dev/nvme1n1 4k
> + fio --bs=4k --ioengine=io_uring --fixedbufs --registerfiles --hipri --iodepth=64 --iodepth_batch_submit=16 --iodepth_batch_complete_min=16 --filename=/dev/nvme1n1 --direct=1 --runtime=10 --numjobs=1 --rw=randread --name=test --group_reporting
> test: (g=0): rw=randread, bs=(R) 4096B-4096B, (W) 4096B-4096B, (T) 4096B-4096B, ioengine=io_uring, iodepth=64
> fio-3.27
> Starting 1 process
> Jobs: 1 (f=1): [r(1)][100.0%][r=1503MiB/s][r=385k IOPS][eta 00m:00s]
> test: (groupid=0, jobs=1): err= 0: pid=3143: Wed Jul 21 05:58:14 2021
>    read: IOPS=384k, BW=1501MiB/s (1573MB/s)(14.7GiB/10001msec)

I am not sure what baseline you used previously, but you were getting 
327K then, so at least this would be an improvement.

> 
> [root at ampere-mtjade-04 ~]# taskset -c 80 ~/git/tools/test/nvme/io_uring 10 1 /dev/nvme1n1 4k
> + fio --bs=4k --ioengine=io_uring --fixedbufs --registerfiles --hipri --iodepth=64 --iodepth_batch_submit=16 --iodepth_batch_complete_min=16 --filename=/dev/nvme1n1 --direct=1 --runtime=10 --numjobs=1 --rw=randread --name=test --group_reporting
> test: (g=0): rw=randread, bs=(R) 4096B-4096B, (W) 4096B-4096B, (T) 4096B-4096B, ioengine=io_uring, iodepth=64
> fio-3.27
> Starting 1 process
> Jobs: 1 (f=1): [r(1)][100.0%][r=138MiB/s][r=35.4k IOPS][eta 00m:00s]
> test: (groupid=0, jobs=1): err= 0: pid=3063: Wed Jul 21 05:55:31 2021
>    read: IOPS=35.4k, BW=138MiB/s (145MB/s)(1383MiB/10001msec)

I can try similar on our arm64 board when I get a chance.

Thanks,
John