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

[Ming Lei]

On Wed, Jul 21, 2021 at 12:07:22PM +0100, John Garry wrote:
> 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.

Looks the improvement isn't from your patches, please see the test result on
v5.14-rc2:

[root at ampere-mtjade-04 ~]# uname -a
Linux ampere-mtjade-04.khw4.lab.eng.bos.redhat.com 5.14.0-rc2_linus #3 SMP Thu Jul 22 03:41:24 EDT 2021 aarch64 aarch64 aarch64 GNU/Linux
[root at ampere-mtjade-04 ~]# taskset -c 0 ~/git/tools/test/nvme/io_uring 20 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=20 --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=1489MiB/s][r=381k IOPS][eta 00m:00s]
test: (groupid=0, jobs=1): err= 0: pid=3099: Thu Jul 22 03:53:04 2021
  read: IOPS=381k, BW=1487MiB/s (1559MB/s)(29.0GiB/20001msec)


thanks, 
Ming