linux-kernel - Re: [PATCH 08/10] swiotlb: don't dip into swiotlb pool for coherent allocations

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Message-ID: <20181012170456.GC60150@arrakis.emea.arm.com>
Date:   Fri, 12 Oct 2018 18:04:56 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Christoph Hellwig <hch@....de>
Cc:     Will Deacon <will.deacon@....com>,
        Robin Murphy <robin.murphy@....com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 08/10] swiotlb: don't dip into swiotlb pool for coherent
 allocations

On Mon, Oct 08, 2018 at 10:02:44AM +0200, Christoph Hellwig wrote:
> All architectures that support swiotlb also have a zone that backs up
> these less than full addressing allocations (usually ZONE_DMA32).
> 
> Because of that it is rather pointless to fall back to the global swiotlb
> buffer if the normal dma direct allocation failed - the only thing this
> will do is to eat up bounce buffers that would be more useful to serve
> streaming mappings.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
>  arch/arm64/mm/dma-mapping.c |   6 +--
>  include/linux/swiotlb.h     |   5 --
>  kernel/dma/swiotlb.c        | 105 +-----------------------------------
>  3 files changed, 5 insertions(+), 111 deletions(-)

Acked-by: Catalin Marinas <catalin.marinas@....com>