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Date: Wed, 14 Apr 2021 15:08:53 +0800
From: Xingang Wang <wangxingang5@...wei.com>
To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@...wei.com>,
"Eric Auger" <eric.auger@...hat.com>,
"eric.auger.pro@...il.com" <eric.auger.pro@...il.com>,
"jean-philippe@...aro.org" <jean-philippe@...aro.org>,
"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
"kvmarm@...ts.cs.columbia.edu" <kvmarm@...ts.cs.columbia.edu>,
"will@...nel.org" <will@...nel.org>,
"maz@...nel.org" <maz@...nel.org>,
"robin.murphy@....com" <robin.murphy@....com>,
"joro@...tes.org" <joro@...tes.org>,
"alex.williamson@...hat.com" <alex.williamson@...hat.com>,
"tn@...ihalf.com" <tn@...ihalf.com>,
zhukeqian <zhukeqian1@...wei.com>
CC: "jacob.jun.pan@...ux.intel.com" <jacob.jun.pan@...ux.intel.com>,
"yi.l.liu@...el.com" <yi.l.liu@...el.com>,
"zhangfei.gao@...aro.org" <zhangfei.gao@...aro.org>,
"zhangfei.gao@...il.com" <zhangfei.gao@...il.com>,
"vivek.gautam@....com" <vivek.gautam@....com>,
yuzenghui <yuzenghui@...wei.com>,
"nicoleotsuka@...il.com" <nicoleotsuka@...il.com>,
lushenming <lushenming@...wei.com>,
"vsethi@...dia.com" <vsethi@...dia.com>,
"chenxiang (M)" <chenxiang66@...ilicon.com>,
"vdumpa@...dia.com" <vdumpa@...dia.com>,
jiangkunkun <jiangkunkun@...wei.com>, <cenjiahui@...wei.com>,
<xieyingtai@...wei.com>
Subject: Re: [PATCH v15 00/12] SMMUv3 Nested Stage Setup (IOMMU part)
Hi Shameer,
On 2021/4/14 14:56, Shameerali Kolothum Thodi wrote:
>
>
>> -----Original Message-----
>> From: wangxingang
>> Sent: 14 April 2021 03:36
>> To: Eric Auger <eric.auger@...hat.com>; eric.auger.pro@...il.com;
>> jean-philippe@...aro.org; iommu@...ts.linux-foundation.org;
>> linux-kernel@...r.kernel.org; kvm@...r.kernel.org;
>> kvmarm@...ts.cs.columbia.edu; will@...nel.org; maz@...nel.org;
>> robin.murphy@....com; joro@...tes.org; alex.williamson@...hat.com;
>> tn@...ihalf.com; zhukeqian <zhukeqian1@...wei.com>
>> Cc: jacob.jun.pan@...ux.intel.com; yi.l.liu@...el.com; zhangfei.gao@...aro.org;
>> zhangfei.gao@...il.com; vivek.gautam@....com; Shameerali Kolothum
>> Thodi <shameerali.kolothum.thodi@...wei.com>; yuzenghui
>> <yuzenghui@...wei.com>; nicoleotsuka@...il.com; lushenming
>> <lushenming@...wei.com>; vsethi@...dia.com; chenxiang (M)
>> <chenxiang66@...ilicon.com>; vdumpa@...dia.com; jiangkunkun
>> <jiangkunkun@...wei.com>
>> Subject: Re: [PATCH v15 00/12] SMMUv3 Nested Stage Setup (IOMMU part)
>>
>> Hi Eric, Jean-Philippe
>>
>> On 2021/4/11 19:12, Eric Auger wrote:
>>> SMMUv3 Nested Stage Setup (IOMMU part)
>>>
>>> This series brings the IOMMU part of HW nested paging support
>>> in the SMMUv3. The VFIO part is submitted separately.
>>>
>>> This is based on Jean-Philippe's
>>> [PATCH v14 00/10] iommu: I/O page faults for SMMUv3
>>> https://www.spinics.net/lists/arm-kernel/msg886518.html
>>> (including the patches that were not pulled for 5.13)
>>>
>>> The IOMMU API is extended to support 2 new API functionalities:
>>> 1) pass the guest stage 1 configuration
>>> 2) pass stage 1 MSI bindings
>>>
>>> Then those capabilities gets implemented in the SMMUv3 driver.
>>>
>>> The virtualizer passes information through the VFIO user API
>>> which cascades them to the iommu subsystem. This allows the guest
>>> to own stage 1 tables and context descriptors (so-called PASID
>>> table) while the host owns stage 2 tables and main configuration
>>> structures (STE).
>>>
>>> Best Regards
>>>
>>> Eric
>>>
>>> This series can be found at:
>>> v5.12-rc6-jean-iopf-14-2stage-v15
>>> (including the VFIO part in its last version: v13)
>>>
>>
>> I am testing the performance of an accelerator with/without SVA/vSVA,
>> and found there might be some potential performance loss risk for SVA/vSVA.
>>
>> I use a Network and computing encryption device (SEC), and send 1MB
>> request for 10000 times.
>>
>> I trigger mm fault before I send the request, so there should be no iopf.
>>
>> Here's what I got:
>>
>> physical scenario:
>> performance: SVA:9MB/s NOSVA:9MB/s
>> tlb_miss: SVA:302,651 NOSVA:1,223
>> trans_table_walk_access:SVA:302,276 NOSVA:1,237
>>
>> VM scenario:
>> performance: vSVA:9MB/s NOvSVA:6MB/s about 30~40% loss
>> tlb_miss: vSVA:4,423,897 NOvSVA:1,907
>> trans_table_walk_access:vSVA:61,928,430 NOvSVA:21,948
>>
>> In physical scenario, there's almost no performance loss, but the
>> tlb_miss and trans_table_walk_access of stage 1 for SVA is quite high,
>> comparing to NOSVA.
>>
>> In VM scenario, there's about 30~40% performance loss, this is because
>> the two stage tlb_miss and trans_table_walk_access is even higher, and
>> impact the performance.
>>
>> I compare the procedure of building page table of SVA and NOSVA, and
>> found that NOSVA uses 2MB mapping as far as possible, while SVA uses
>> only 4KB.
>>
>> I retest with huge page, and huge page could solve this problem, the
>> performance of SVA/vSVA is almost the same as NOSVA.
>>
>> I am wondering do you have any other solution for the performance loss
>> of vSVA, or any other method to reduce the tlb_miss/trans_table_walk.
>
> Hi Xingang,
>
> Just curious, do you have DVM enabled on this board or does it use explicit
> SMMU TLB invalidations?
>
> Thanks,
> Shameer
>
For now, DVM is enabled and TLBI is not explicit used.
And by the way the performance data above is
performance: vSVA:9GB/s(not 9MB/s) NOvSVA:6GB/s(not 6GB/s)
Thanks
Xingang
.
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