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

[Ming Lei <ming.lei@redhat.com>]

On Thu, Jul 22, 2021 at 11:05:00AM +0100, John Garry wrote:
> On 22/07/2021 08:58, Ming Lei wrote:
> > 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@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@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@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@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)
> 
> I'm a bit surprised at that.
> 
> Anyway, I don't see such an issue as you are seeing on my system. In
> general, running from different nodes doesn't make a huge difference. But
> note that the NVMe device is on NUMA node #2 on my 4-node system. I assume
> that the IOMMU is also located in that node.
> 
> sudo taskset -c 0 fio/fio --bs=4k --ioengine=io_uring --fixedbufs
> --registerfiles --hipri --iodepth=64 --iodepth_batch_submit=16
> --iodepth_batch_complete_min=16 --filename=/dev/nvme0n1 --direct=1
> --runtime=20 --numjobs=1 --rw=randread --name=test --group_reporting
> 
>  read: IOPS=479k
> 
> ---
> sudo taskset -c 4 fio/fio --bs=4k --ioengine=io_uring --fixedbufs
> --registerfiles --hipri --iodepth=64 --iodepth_batch_submit=16
> --iodepth_batch_complete_min=16 --filename=/dev/nvme0n1 --direct=1
> --runtime=20 --numjobs=1 --rw=randread --name=test --group_reporting
> 
>  read: IOPS=307k
> 
> ---
> sudo taskset -c 32 fio/fio --bs=4k --ioengine=io_uring --fixedbufs
> --registerfiles --hipri --iodepth=64 --iodepth_batch_submit=16
> --iodepth_batch_complete_min=16 --filename=/dev/nvme0n1 --direct=1
> --runtime=20 --numjobs=1 --rw=randread --name=test --group_reporting
> 
> read: IOPS=566k
> 
> --
> sudo taskset -c 64 fio/fio --bs=4k --ioengine=io_uring --fixedbufs
> --registerfiles --hipri --iodepth=64 --iodepth_batch_submit=16
> --iodepth_batch_complete_min=16 --filename=/dev/nvme0n1 --direct=1
> --runtime=20 --numjobs=1 --rw=randread --name=test --group_reporting
> 
> read: IOPS=488k
> 
> ---
> sudo taskset -c 96 fio/fio --bs=4k --ioengine=io_uring --fixedbufs
> --registerfiles --hipri --iodepth=64 --iodepth_batch_submit=16
> --iodepth_batch_complete_min=16 --filename=/dev/nvme0n1 --direct=1
> --runtime=20 --numjobs=1 --rw=randread --name=test --group_reporting
> 
>  read: IOPS=508k
> 
> 
> If you check below, you can see that cpu4 services an NVMe irq. From
> checking htop, during the test that cpu is at 100% load, which I put the
> performance drop (vs cpu0) down to.

nvme.poll_queues is 2 in my test, and no irq is involved. But the irq mode
fio test is still as bad as io_uring.

> 
> Here's some system info:
> 
> HW queue irq affinities:
> PCI name is 81:00.0: nvme0n1
> -eirq 298, cpu list 67, effective list 67
> -eirq 299, cpu list 32-38, effective list 35
> -eirq 300, cpu list 39-45, effective list 39
> -eirq 301, cpu list 46-51, effective list 46
> -eirq 302, cpu list 52-57, effective list 52
> -eirq 303, cpu list 58-63, effective list 60
> -eirq 304, cpu list 64-69, effective list 68
> -eirq 305, cpu list 70-75, effective list 70
> -eirq 306, cpu list 76-80, effective list 76
> -eirq 307, cpu list 81-85, effective list 84
> -eirq 308, cpu list 86-90, effective list 86
> -eirq 309, cpu list 91-95, effective list 92
> -eirq 310, cpu list 96-101, effective list 100
> -eirq 311, cpu list 102-107, effective list 102
> -eirq 312, cpu list 108-112, effective list 108
> -eirq 313, cpu list 113-117, effective list 116
> -eirq 314, cpu list 118-122, effective list 118
> -eirq 315, cpu list 123-127, effective list 124
> -eirq 316, cpu list 0-5, effective list 4
> -eirq 317, cpu list 6-11, effective list 6
> -eirq 318, cpu list 12-16, effective list 12
> -eirq 319, cpu list 17-21, effective list 20
> -eirq 320, cpu list 22-26, effective list 22
> -eirq 321, cpu list 27-31, effective list 28
> 
> 
> john@ubuntu:~$ lscpu | grep NUMA
> NUMA node(s):  4
> NUMA node0 CPU(s):   0-31
> NUMA node1 CPU(s):   32-63
> NUMA node2 CPU(s):   64-95
> NUMA node3 CPU(s):   96-127
> 
> john@ubuntu:~$ lspci | grep -i non
> 81:00.0 Non-Volatile memory controller: Huawei Technologies Co., Ltd. Device
> 0123 (rev 45)
> 
> cat /sys/block/nvme0n1/device/device/numa_node
> 2

BTW, nvme driver doesn't apply the pci numa node, and I guess the
following patch is needed:

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 11779be42186..3c5e10e8b0c2 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -4366,7 +4366,11 @@ int nvme_init_ctrl(struct nvme_ctrl *ctrl, struct device *dev,
 	ctrl->dev = dev;
 	ctrl->ops = ops;
 	ctrl->quirks = quirks;
+#ifdef CONFIG_NUMA
+	ctrl->numa_node = dev->numa_node;
+#else
 	ctrl->numa_node = NUMA_NO_NODE;
+#endif
 	INIT_WORK(&ctrl->scan_work, nvme_scan_work);
 	INIT_WORK(&ctrl->async_event_work, nvme_async_event_work);
 	INIT_WORK(&ctrl->fw_act_work, nvme_fw_act_work);

> 
> [   52.968495] nvme 0000:81:00.0: Adding to iommu group 5
> [   52.980484] nvme nvme0: pci function 0000:81:00.0
> [   52.999881] nvme nvme0: 23/0/0 default/read/poll queues

Looks you didn't enabling polling. In irq mode, it isn't strange
to observe IOPS difference when running fio on different CPUs.

Thanks,
Ming