From: John Garry <john.garry@huawei.com>
To: Robin Murphy <robin.murphy@arm.com>,
Ming Lei <ming.lei@redhat.com>, <linux-nvme@lists.infradead.org>,
Will Deacon <will@kernel.org>,
<linux-arm-kernel@lists.infradead.org>,
<iommu@lists.linux-foundation.org>
Cc: <linux-kernel@vger.kernel.org>
Subject: Re: [bug report] iommu_dma_unmap_sg() is very slow then running IO from remote numa node
Date: Fri, 9 Jul 2021 12:04:24 +0100 [thread overview]
Message-ID: <a44e8a68-d789-e3db-4fbb-404defb431f6@huawei.com> (raw)
In-Reply-To: <23e7956b-f3b5-b585-3c18-724165994051@arm.com>
On 09/07/2021 11:26, Robin Murphy wrote:
> n 2021-07-09 09:38, Ming Lei wrote:
>> Hello,
>>
>> I observed that NVMe performance is very bad when running fio on one
>> CPU(aarch64) in remote numa node compared with the nvme pci numa node.
>>
>> Please see the test result[1] 327K vs. 34.9K.
>>
>> Latency trace shows that one big difference is in iommu_dma_unmap_sg(),
>> 1111 nsecs vs 25437 nsecs.
>
> Are you able to dig down further into that? iommu_dma_unmap_sg() itself
> doesn't do anything particularly special, so whatever makes a difference
> is probably happening at a lower level, and I suspect there's probably
> an SMMU involved. If for instance it turns out to go all the way down to
> __arm_smmu_cmdq_poll_until_consumed() because polling MMIO from the
> wrong node is slow, there's unlikely to be much you can do about that
> other than the global "go faster" knobs (iommu.strict and
> iommu.passthrough) with their associated compromises.
There was also the disable_msipolling option:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c#n42
But I am not sure if that platform even supports MSI polling (or has
smmu v3).
You could also try iommu.forcedac=1 cmdline option. But I doubt it will
help since the issue was mentioned to be NUMA related.
>
> Robin.
>
>> [1] fio test & results
>>
>> 1) fio test result:
>>
>> - run fio on local CPU
>> 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
>>
>> IOPS: 327K
>> avg latency of iommu_dma_unmap_sg(): 1111 nsecs
>>
>>
>> - run fio on remote CPU
>> 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
>>
>> IOPS: 34.9K
>> avg latency of iommu_dma_unmap_sg(): 25437 nsecs
>>
>> 2) system info
>> [root@ampere-mtjade-04 ~]# lscpu | grep NUMA
>> NUMA node(s): 2
>> NUMA node0 CPU(s): 0-79
>> NUMA node1 CPU(s): 80-159
>>
>> lspci | grep NVMe
>> 0003:01:00.0 Non-Volatile memory controller: Samsung Electronics Co
>> Ltd NVMe SSD Controller SM981/PM981/PM983
>>
>> [root@ampere-mtjade-04 ~]# cat /sys/block/nvme1n1/device/device/numa_node
Since it's ampere, I guess it's smmu v3.
BTW, if you remember, I did raise a performance issue of smmuv3 with
NVMe before:
https://lore.kernel.org/linux-iommu/b2a6e26d-6d0d-7f0d-f222-589812f701d2@huawei.com/
I did have this series to improve performance for systems with lots of
CPUs, like above, but not accepted:
https://lore.kernel.org/linux-iommu/1598018062-175608-1-git-send-email-john.garry@huawei.com/
Thanks,
John
next prev parent reply other threads:[~2021-07-09 11:11 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-09 8:38 [bug report] iommu_dma_unmap_sg() is very slow then running IO from remote numa node Ming Lei
2021-07-09 10:16 ` Russell King (Oracle)
2021-07-09 14:21 ` Ming Lei
2021-07-09 10:26 ` Robin Murphy
2021-07-09 11:04 ` John Garry [this message]
2021-07-09 12:34 ` Robin Murphy
2021-07-09 14:24 ` Ming Lei
2021-07-19 16:14 ` John Garry
2021-07-21 1:40 ` Ming Lei
2021-07-21 9:23 ` John Garry
2021-07-21 9:59 ` Ming Lei
2021-07-21 11:07 ` John Garry
2021-07-21 11:58 ` Ming Lei
2021-07-22 7:58 ` Ming Lei
2021-07-22 10:05 ` John Garry
2021-07-22 10:19 ` Ming Lei
2021-07-22 11:12 ` John Garry
2021-07-22 12:53 ` Marc Zyngier
2021-07-22 13:54 ` John Garry
2021-07-22 15:54 ` Ming Lei
2021-07-22 17:40 ` Robin Murphy
2021-07-23 10:21 ` Ming Lei
2021-07-26 7:51 ` John Garry
2021-07-28 1:32 ` Ming Lei
2021-07-28 10:38 ` John Garry
2021-07-28 15:17 ` Ming Lei
2021-07-28 15:39 ` Robin Murphy
2021-08-10 9:36 ` John Garry
2021-08-10 10:35 ` Ming Lei
2021-07-27 17:08 ` Robin Murphy
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