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Re: [PATCH V2] x86/tboot: add an option to disable iommu force on

From Joerg Roedel <jroedel@suse.de>
Newsgroups linux.kernel
Subject Re: [PATCH V2] x86/tboot: add an option to disable iommu force on
Date 2017-04-27 17:20 +0200
Message-ID <tATn4-2pt-17@gated-at.bofh.it> (permalink)
References <tAxPA-4Ed-13@gated-at.bofh.it> <tALzb-5ht-11@gated-at.bofh.it> <tANhE-6ta-13@gated-at.bofh.it> <tATn4-2pt-19@gated-at.bofh.it>
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On Thu, Apr 27, 2017 at 07:49:02AM -0700, Shaohua Li wrote:
> This is exactly the usage for us. And please note, not everybody should
> sacrifice the DMA security. It is only required when the pcie device hits iommu
> hardware limitation. In our enviroment, normal network workloads (as high as
> 60k pps) are completely ok with iommu enabled. Only the XDP workload, which can
> do around 200k pps, is suffering from the problem. So completely forcing iommu
> off for some workloads without the performance issue isn't good because of the
> DMA security.

How big are the packets in your XDP workload? I also run pps tests for
performance measurement on older desktop-class hardware
(Xeon E5-1620 v2 and AMD FX 6100) and 10GBit network
hardware, and easily get over the 200k pps mark with IOMMU enabled. The
Intel system can receive >900k pps and the AMD system is still at
~240k pps.

But my tests only send IPv4/UDP packets with 8bytes of payload, so that
is probably different to your setup.



	Joerg

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Thread

[PATCH V2] x86/tboot: add an option to disable iommu force on Shaohua Li <shli@fb.com> - 2017-04-26 18:20 +0200
  Re: [PATCH V2] x86/tboot: add an option to disable iommu force on Joerg Roedel <jroedel@suse.de> - 2017-04-27 00:10 +0200
    Re: [PATCH V2] x86/tboot: add an option to disable iommu force on Ingo Molnar <mingo@kernel.org> - 2017-04-27 09:00 +0200
      Re: [PATCH V2] x86/tboot: add an option to disable iommu force on Joerg Roedel <jroedel@suse.de> - 2017-04-29 00:20 +0200
  Re: [PATCH V2] x86/tboot: add an option to disable iommu force on Ingo Molnar <mingo@kernel.org> - 2017-04-27 09:00 +0200
    Re: [PATCH V2] x86/tboot: add an option to disable iommu force on Joerg Roedel <jroedel@suse.de> - 2017-04-27 10:50 +0200
      Re: [PATCH V2] x86/tboot: add an option to disable iommu force on Joerg Roedel <jroedel@suse.de> - 2017-04-27 17:20 +0200
        Re: [PATCH V2] x86/tboot: add an option to disable iommu force on Joerg Roedel <jroedel@suse.de> - 2017-04-27 18:10 +0200
      Re: [PATCH V2] x86/tboot: add an option to disable iommu force on Ingo Molnar <mingo@kernel.org> - 2017-05-05 09:00 +0200
        Re: [PATCH V2] x86/tboot: add an option to disable iommu force on Joerg Roedel <jroedel@suse.de> - 2017-05-05 10:50 +0200
          Re: [PATCH V2] x86/tboot: add an option to disable iommu force on Ingo Molnar <mingo@kernel.org> - 2017-05-06 11:50 +0200

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