linux-kernel - Re: [PATCH 1/4] iommu/arm-smmu-v3: Use command queue batching helpers to improve performance

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Date:   Mon, 16 Aug 2021 09:21:27 +0100
From:   Will Deacon <will@...nel.org>
To:     "Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>
Cc:     John Garry <john.garry@...wei.com>,
        Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        iommu <iommu@...ts.linux-foundation.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] iommu/arm-smmu-v3: Use command queue batching
 helpers to improve performance

On Mon, Aug 16, 2021 at 03:47:58PM +0800, Leizhen (ThunderTown) wrote:
> 
> 
> On 2021/8/16 15:24, John Garry wrote:
> >> In addition, I find that function arm_smmu_cmdq_build_cmd() can also be optimized
> >> slightly, three useless instructions can be reduced.
> > 
> > I think that you could optimise further by pre-building commonly used commands.
> > 
> > For example, CMD_SYNC without MSI polling is always the same. And then only different in 1 field for MSI polling.
> > 
> > But you need to check if the performance gain is worth the change.
> 
> Good advice. I can give it a try.

Please send it as a new patch on top. I've queued the old one and sent
it to Joerg. Since this is just further cleanup, it can be done separately.

Will