linux-kernel - Re: [PATCH V3 0/2] iommu/arm-smmu-v3: Add support for ECMDQ register mode

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Message-ID: <b1706177-051d-8a82-97a8-3b482be353af@huaweicloud.com>
Date: Sun, 28 Apr 2024 10:08:28 +0800
From: "Leizhen (ThunderTown)" <thunder.leizhen@...weicloud.com>
To: Tanmay Jagdale <tanmay@...vell.com>, will@...nel.org,
 robin.murphy@....com, joro@...tes.org, nicolinc@...dia.com,
 mshavit@...gle.com, baolu.lu@...ux.intel.com, thunder.leizhen@...wei.com,
 set_pte_at@...look.com, smostafa@...gle.com
Cc: sgoutham@...vell.com, gcherian@...vell.com, jcm@...masters.org,
 linux-arm-kernel@...ts.infradead.org, iommu@...ts.linux.dev,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH V3 0/2] iommu/arm-smmu-v3: Add support for ECMDQ register
 mode



On 2024/4/25 22:41, Tanmay Jagdale wrote:
> Resending the patches by Zhen Lei <thunder.leizhen@...wei.com> that add
> support for SMMU ECMDQ feature.
> 
> Tested this feature on a Marvell SoC by implementing a smmu-test driver.
> This test driver spawns a thread per CPU and each thread keeps sending
> map, table-walk and unmap requests for a fixed duration.
> 
> Using this test driver, we compared ECMDQ vs SMMU with software batching
> support and saw ~5% improvement with ECMDQ. Performance numbers are

This data is similar to the performance simulated by our EMU.

> mentioned below:
> 
>                    Total Requests  Average Requests  Difference
>                                       Per CPU         wrt ECMDQ
> -----------------------------------------------------------------
> ECMDQ                 239286381       2991079
> CMDQ Batch Size 1     228232187       2852902         -4.62%
> CMDQ Batch Size 32    233465784       2918322         -2.43%
> CMDQ Batch Size 64    231679588       2895994         -3.18%
> CMDQ Batch Size 128   233189030       2914862         -2.55%
> CMDQ Batch Size 256   230965773       2887072         -3.48%
> 
> 
> v2 --> v3:
> 1. Rebased on linux 6.9-rc5
> 
> v1 --> v2:

Thanks.

> 1. Drop patch "iommu/arm-smmu-v3: Add arm_smmu_ecmdq_issue_cmdlist() for
> non-shared ECMDQ" in v1
> 2. Drop patch "iommu/arm-smmu-v3: Add support for less than one ECMDQ
> per core" in v1
> 3. Replace rwlock with IPI to support lockless protection against the
> write operation to bit
>    'ERRACK' during error handling and the read operation to bit 'ERRACK'
> during command insertion. 
> 4. Standardize variable names.
> -	struct arm_smmu_ecmdq *__percpu	*ecmdq;
> +	struct arm_smmu_ecmdq *__percpu	*ecmdqs;
> 
> 5. Add member 'iobase' to struct arm_smmu_device to record the start
> physical
>    address of the SMMU, to replace translation operation
> (vmalloc_to_pfn(smmu->base) << PAGE_SHIFT)
> +	phys_addr_t			iobase;
> -	smmu_dma_base = (vmalloc_to_pfn(smmu->base) << PAGE_SHIFT);
> 
> 6. Cancel below union. Whether ECMDQ is enabled is determined only based
> on 'ecmdq_enabled'.
> -	union {
> -		u32			nr_ecmdq;
> -		u32			ecmdq_enabled;
> -	};
> +	u32				nr_ecmdq;
> +	bool				ecmdq_enabled;
> 
> 7. Eliminate some sparse check warnings. For example.
> -	struct arm_smmu_ecmdq *ecmdq;
> +	struct arm_smmu_ecmdq __percpu *ecmdq;
> 
> 
> Zhen Lei (2):
>   iommu/arm-smmu-v3: Add support for ECMDQ register mode
>   iommu/arm-smmu-v3: Ensure that a set of associated commands are
>     inserted in the same ECMDQ
> 
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 261 +++++++++++++++++++-
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h |  33 +++
>  2 files changed, 286 insertions(+), 8 deletions(-)
> 

-- 
Regards,
  Zhen Lei