linux-kernel - Re: [PATCHv5] iommu/arm-smmu: Optimize ->tlb_flush

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Message-Id: <162886044327.2821414.7990736519109651727.b4-ty@kernel.org>
Date:   Fri, 13 Aug 2021 15:33:48 +0100
From:   Will Deacon <will@...nel.org>
To:     Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>,
        Joerg Roedel <joro@...tes.org>,
        Robin Murphy <robin.murphy@....com>
Cc:     catalin.marinas@....com, kernel-team@...roid.com,
        Will Deacon <will@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Tomasz Figa <tfiga@...omium.org>,
        linux-arm-msm@...r.kernel.org,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Krishna Reddy <vdumpa@...dia.com>,
        iommu@...ts.linux-foundation.org,
        Doug Anderson <dianders@...omium.org>,
        Thierry Reding <treding@...dia.com>
Subject: Re: [PATCHv5] iommu/arm-smmu: Optimize ->tlb_flush_walk() for qcom implementation

On Wed, 11 Aug 2021 21:34:26 +0530, Sai Prakash Ranjan wrote:
> Currently for iommu_unmap() of large scatter-gather list with page size
> elements, the majority of time is spent in flushing of partial walks in
> __arm_lpae_unmap() which is a VA based TLB invalidation invalidating
> page-by-page on iommus like arm-smmu-v2 (TLBIVA).
> 
> For example: to unmap a 32MB scatter-gather list with page size elements
> (8192 entries), there are 16->2MB buffer unmaps based on the pgsize (2MB
> for 4K granule) and each of 2MB will further result in 512 TLBIVAs (2MB/4K)
> resulting in a total of 8192 TLBIVAs (512*16) for 16->2MB causing a huge
> overhead.
> 
> [...]

Applied to will (for-joerg/arm-smmu/updates), thanks!

[1/1] iommu/arm-smmu: Optimize ->tlb_flush_walk() for qcom implementation
      https://git.kernel.org/will/c/ef75702d6d65

Cheers,
-- 
Will

https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev