Re: [bug report] iommu_dma_unmap_sg() is very slow then running IO from remote numa node
From: Ming Lei <hidden>
Date: 2021-07-28 15:17:41
Also in:
linux-iommu, linux-nvme, lkml
On Wed, Jul 28, 2021 at 11:38:18AM +0100, John Garry wrote:
On 28/07/2021 02:32, Ming Lei wrote:quoted
On Mon, Jul 26, 2021 at 3:51 PM John Garry[off-list ref] wrote:quoted
On 23/07/2021 11:21, Ming Lei wrote:quoted
quoted
Thanks, I was also going to suggest the latter, since it's what arm_smmu_cmdq_issue_cmdlist() does with IRQs masked that should be most indicative of where the slowness most likely stems from.The improvement from 'iommu.strict=0' is very small:Have you tried turning off the IOMMU to ensure that this is really just an IOMMU problem? You can try setting CONFIG_ARM_SMMU_V3=n in the defconfig or passing cmdline param iommu.passthrough=1 to bypass the the SMMU (equivalent to disabling for kernel drivers).Bypassing SMMU via iommu.passthrough=1 basically doesn't make a difference on this issue.A ~90% throughput drop still seems to me to be too high to be a software issue. More so since I don't see similar on my system. And that throughput drop does not lead to a total CPU usage drop, from the fio log. Do you know if anyone has run memory benchmark tests on this board to find out NUMA effect? I think lmbench or stream could be used for this.
https://lore.kernel.org/lkml/YOhbc5C47IzC893B@T590/ (local) -- Ming _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel