Comment 6 for bug 1688158

On Fri, May 12, 2017 at 9:06 AM, Jeff Hugo <email address hidden>
wrote:
> Just FYI, it will likely take me a few days to get to this.

Thanks Jeff, no problem.

>
> Jeffrey Hugo
> Senior Engineer
> Qualcomm Datacenter Technologies, Inc.
> 1-303-247-5002
>
> From: Manoj Iyer [mailto:<email address hidden>]
> Sent: Thursday, May 11, 2017 9:23 PM
> To: Jeff Hugo <email address hidden>; <email address hidden>
> Cc: Nate Watterson <email address hidden>; Timur Tabi
> <email address hidden>
> Subject: [Bug #1688158] Please help test kernel for
> iommu.passthrough=0/1
>
> Jeff,
>
> I have back-ported patches to address "Support SMMU passthrough using
> the default domain". This adds a new kernel command line option
> iommu.passthrough=0/1 to Configure DMA to bypass the IOMMU for ARM64.
> http://bugs.launchpad.net/bugs/1688158
>
> 0 - Use IOMMU translation for DMA.
> 1 - Bypass the IOMMU for DMA.
>
> The test case recommended by Nate using 'fio' is:
>
> $ sudo apt update ; sudo apt install fio
>
> $ sudo fio --name=global --readonly --group_reporting --direct=1
> --ioengine=libaio --rw=read --eta-newline=1s --size=1T
> --blocksize=512k --iodepth=32 --numjobs=1 --runtime=10s
> --name=nvme_0 --filename=/dev/nvme0n1
>
> You can find the kernel and the instructions to install the kernel in
> the Centriq test PPA:
> https://launchpad.net/~centriq-team/+archive/ubuntu/test/
>
> Nate and I have gone back and forth on testing these patches and
> finally came down to having this test run on an NVME device.
> Unfortunately I cant seem to find any nvme HW at this time, we would
> need to order these drive and could take time.
>
> Could you please test the kernel using the test case mentioned above
> and reply back to this email with test case out put for both cases.
> iommu.passthrough=0 and iommu.passthrough=1. We should see better
> performance (iops may be) with IOMMU bypassed for DMA (ie
> iommu.passthrough=1).
>
> The bug is cced on this email, so if you replay with a summary output
> in both cases it will be automatically recorded in the bug. Once I
> get your test results I will be able to make a case for SRUing these
> patches.
>
> Thanks a ton
> Manoj Iyer