From: Christoph Hellwig <hch@lst.de>
To: Ricardo Ribalda <ribalda@chromium.org>
Cc: Christoph Hellwig <hch@lst.de>, Tomasz Figa <tfiga@chromium.org>,
Mauro Carvalho Chehab <mchehab@kernel.org>,
Marek Szyprowski <m.szyprowski@samsung.com>,
"list@263.net:IOMMU DRIVERS <iommu@lists.linux-foundation.org>,
Joerg Roedel <joro@8bytes.org>,"
<iommu@lists.linux-foundation.org>,
Robin Murphy <robin.murphy@arm.com>,
Linux Doc Mailing List <linux-doc@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux Media Mailing List <linux-media@vger.kernel.org>
Subject: Re: [PATCH 8/8] WIP: add a dma_alloc_contiguous API
Date: Tue, 10 Nov 2020 10:41:23 +0100 [thread overview]
Message-ID: <20201110094123.GA25672@lst.de> (raw)
In-Reply-To: <CANiDSCsBUBV1WA2To9x26Uhc5SU-4xuh3m4wUwXBcGwA6n8now@mail.gmail.com>
On Tue, Nov 10, 2020 at 10:33:05AM +0100, Ricardo Ribalda wrote:
> Also FYI, I managed to boot an ARM device with that tree. But I could
> not test the uvc driver (it was a remote device with no usb device
> attached)
>
> Hopefully I will be able to test it for real this week.
>
> Any suggestions for how to measure performance difference?
I have to admit I don't know at all how uvc works. But the main
problem with dma_alloc_coherent is that all access is uncached. So
anything that does larger and/or many data transfers to and from it
will be glacially slow. With the dma streaming API we still have to
pay for cache flushes, but only before and after the transfers, and
in many cases in a somewhat optimized fashion.
next prev parent reply other threads:[~2020-11-10 9:41 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-30 16:09 dma_alloc_pages / dma_alloc_noncoherent fixups Christoph Hellwig
2020-09-30 16:09 ` [PATCH 1/8] dma-mapping: remove the {alloc,free}_noncoherent methods Christoph Hellwig
2020-09-30 16:09 ` [PATCH 2/8] dma-mapping: document dma_{alloc,free}_pages Christoph Hellwig
2020-09-30 16:09 ` [PATCH 3/8] dma-direct check for highmem pages in dma_direct_alloc_pages Christoph Hellwig
2020-09-30 16:09 ` [PATCH 4/8] dma-direct: use __GFP_ZERO " Christoph Hellwig
2020-09-30 16:09 ` [PATCH 5/8] dma-direct: factor out a dma_direct_alloc_from_pool helper Christoph Hellwig
2020-09-30 16:09 ` [PATCH 6/8] dma-direct: simplify the DMA_ATTR_NO_KERNEL_MAPPING handling Christoph Hellwig
2020-09-30 16:09 ` [PATCH 7/8] dma-iommu: remove __iommu_dma_mmap Christoph Hellwig
2020-09-30 16:09 ` [PATCH 8/8] WIP: add a dma_alloc_contiguous API Christoph Hellwig
2020-10-02 17:50 ` Tomasz Figa
2020-10-05 8:26 ` Christoph Hellwig
2020-10-06 20:56 ` Tomasz Figa
2020-10-07 6:21 ` Christoph Hellwig
2020-10-07 12:21 ` Tomasz Figa
2020-10-07 12:24 ` Christoph Hellwig
2020-10-14 13:20 ` Tomasz Figa
2020-10-14 15:03 ` David Laight
2020-11-09 14:53 ` Ricardo Ribalda
2020-11-10 9:25 ` Christoph Hellwig
2020-11-10 9:33 ` Ricardo Ribalda
2020-11-10 9:41 ` Christoph Hellwig [this message]
2020-11-10 9:50 ` Tomasz Figa
2020-11-10 9:57 ` Christoph Hellwig
2020-11-17 21:21 ` Ricardo Ribalda
2020-11-18 14:25 ` [PATCH] WIP! media: uvcvideo: Use dma_alloc_noncontiguos API Ricardo Ribalda
2020-11-24 11:35 ` Christoph Hellwig
2020-11-24 12:01 ` Ricardo Ribalda
2020-11-24 13:33 ` Christoph Hellwig
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