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

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Date: Thu, 16 May 2024 07:25:39 -0700
From: Tanmay Jagdale <tj@...0ka.smtp.subspace.kernel.org>
To: Will Deacon <will@...nel.org>
CC: Tanmay Jagdale <tanmay@...vell.com>, <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>,
        <sgoutham@...vell.com>, <gcherian@...vell.com>, <gakula@...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

Hi Will,

On Tue, Apr 30, 2024 at 04:09:50PM +0100, Will Deacon wrote:
> On Thu, Apr 25, 2024 at 07:41:50AM -0700, 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
> > 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%
> 
> These are pretty small improvements in a targetted micro-benchmark. Do
> you have any real-world numbers showing that this is worthwhile? For
> example, running something like netperf.
We are running benchmarks on the latest kernel with and without ECMDQ.
We will share the performance numbers and observations here.

With Regards,
Tanmay
> 
> Will
> 
> _______________________________________________
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> linux-arm-kernel@...ts.infradead.org
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