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From: "Dan Williams" <dan.j.williams@intel.com>
To: "Haavard Skinnemoen" <hskinnemoen@atmel.com>
Cc: linux-kernel@vger.kernel.org,
"Shannon Nelson" <shannon.nelson@intel.com>,
"David Brownell" <david-b@pacbell.net>,
kernel@avr32linux.org, "Francis Moreau" <francis.moro@gmail.com>,
"Paul Mundt" <lethal@linux-sh.org>,
"Vladimir A. Barinov" <vbarinov@ru.mvista.com>,
"Pierre Ossman" <drzeus-list@drzeus.cx>
Subject: Re: [RFC v2 4/5] dmaengine: Driver for the Synopsys DesignWare DMA controller
Date: Wed, 30 Jan 2008 11:53:24 -0700 [thread overview]
Message-ID: <e9c3a7c20801301053p7279b660g8f967120d0d16bf5@mail.gmail.com> (raw)
In-Reply-To: <1201630213-31900-5-git-send-email-hskinnemoen@atmel.com>
On Jan 29, 2008 11:10 AM, Haavard Skinnemoen <hskinnemoen@atmel.com> wrote:
[..]
> The dmatest client shows no problems, but the performance is not as
> good as it should be yet -- iperf shows a slight slowdown when
> enabling TCP receive copy offload. This is probably because the
> controller is set up to always do byte transfers; I'll try to optimize
> this, but if someone can tell me if there any guaranteed alignment
> requirements for the users of the DMA engine API, that would help a
> lot.
>
dmaengine punts to the dma-mapping api. So no, there are no alignment
guarantees. The performance loss is probably more related to the
cache synchronization overkill of get_user_pages(). I/O incoherent
architectures end up synchronizing entire pages when we only need to
sync a kilobyte or two in this path.
--
Dan
next prev parent reply other threads:[~2008-01-30 18:53 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-01-29 18:10 [RFC v2 0/5] dmaengine: Slave DMA interface and example users Haavard Skinnemoen
2008-01-29 18:10 ` [RFC v2 1/5] dmaengine: Add dma_client parameter to device_alloc_chan_resources Haavard Skinnemoen
2008-01-29 18:10 ` [RFC v2 2/5] dmaengine: Add slave DMA interface Haavard Skinnemoen
2008-01-29 18:10 ` [RFC v2 3/5] dmaengine: Make DMA Engine menu visible for AVR32 users Haavard Skinnemoen
2008-01-29 18:10 ` [RFC v2 4/5] dmaengine: Driver for the Synopsys DesignWare DMA controller Haavard Skinnemoen
2008-01-29 18:10 ` [RFC v2 5/5] Atmel MCI: Driver for Atmel on-chip MMC controllers Haavard Skinnemoen
2008-02-13 18:30 ` Pierre Ossman
2008-02-13 18:47 ` Haavard Skinnemoen
2008-02-14 14:00 ` MMC core debugfs support (was Re: [RFC v2 5/5] Atmel MCI: Driver for Atmel on-chip MMC controllers) Haavard Skinnemoen
2008-02-25 17:12 ` Pierre Ossman
2008-02-13 19:11 ` [RFC v2 5/5] Atmel MCI: Driver for Atmel on-chip MMC controllers Dan Williams
2008-02-13 21:06 ` Haavard Skinnemoen
2008-02-13 23:55 ` Dan Williams
2008-02-14 8:36 ` Haavard Skinnemoen
2008-02-14 18:34 ` Dan Williams
2008-02-14 19:21 ` Haavard Skinnemoen
2008-01-30 18:53 ` Dan Williams [this message]
2008-01-30 7:30 ` [RFC v2 2/5] dmaengine: Add slave DMA interface David Brownell
2008-01-30 9:27 ` Haavard Skinnemoen
2008-01-30 10:52 ` David Brownell
2008-01-30 12:26 ` Haavard Skinnemoen
2008-01-31 8:27 ` David Brownell
2008-01-31 8:44 ` Paul Mundt
2008-01-31 12:51 ` David Brownell
2008-01-31 14:12 ` Haavard Skinnemoen
2008-01-31 13:52 ` Haavard Skinnemoen
2008-02-06 21:08 ` Dan Williams
2008-02-07 17:56 ` Haavard Skinnemoen
2008-01-30 18:28 ` Dan Williams
2008-01-30 20:45 ` David Brownell
2008-01-31 6:35 ` SDIO driver not receiving responses Farbod Nejati
2008-02-07 19:51 ` Pierre Ossman
2008-01-29 20:54 ` [RFC v2 0/5] dmaengine: Slave DMA interface and example users Haavard Skinnemoen
2008-01-30 6:56 ` David Brownell
2008-01-30 8:56 ` Haavard Skinnemoen
2008-01-30 17:39 ` Dan Williams
2008-02-04 15:32 ` Haavard Skinnemoen
2008-02-06 18:46 ` Dan Williams
2008-02-07 17:52 ` Haavard Skinnemoen
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