Date: Mon, 26 Jul 2010 12:03:51 -0400 From: Greg Ansley <gja@ansley.com> To: "freebsd-arm@FreeBSD.org" <freebsd-arm@FreeBSD.org> Subject: Re: at91sam9g20: Ethernet performance Message-ID: <4C4DB1E7.7090201@ansley.com> In-Reply-To: <20100720023034.GS28908@cicely7.cicely.de> References: <4C444E8B.6090104@ansley.com> <20100719153614.GI28908@cicely7.cicely.de> <AANLkTilj6crfPkCfViYU8LkFxZ6LY8WxRAghiZXaSDn_@mail.gmail.com> <20100719.182202.918765004097971572.imp@bsdimp.com> <20100720023034.GS28908@cicely7.cicely.de>
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Quick (read very very rough) real world numbers using the same (new) if_ate code: "ping -s 1500 -c 1000 -i .006" (from an idle quad core server on a 100BaseT): rm9200: min/avg/max/stddev = 0.826/1.001/2.472/0.063 (if_ate) sam9g20: min/avg/max/stddev = 0.526/0.586/0.892/0.037 (if_ate) While the 9g20 is not blazing it is respectable on a 100Mb link and ~1.7 times faster that the rm9200 even with the receive copies still in place. For reference here are the results from the if_macb driver for sam9 (only) that was committed a few days ago: sam9g20: min/avg/max/stddev = 0.703/0.779/1.000/0.038 (if_macb) Greg On 7/19/10 10:30 PM, Bernd Walter wrote: > The performance has two reasons. > First the fact that the RM9200 ATE can't DMA into non 4-byte aligned > buffers, which requires copying and memory bandwidth is rather slow, > which especially sucks because of the required copy'ing. > IP headers are no n*4 bytes, so you want a 2 byte offset in your > receive buffers otherwise IP code copy'es received buffers. > On sending AFAIK the ATE driver copy'es data into 4 alignment. > The memory interface on SAM9 is much faster because it is DDR, > higher clocked and with it's bus matrix e.g. DMA can access DDRAM > and CPU IO in parallel. > I don't see a technical reason to have different source files. > A few things can be tuned on compiletime, but this is only > a win to save code size - from the runtime point a few rev-checks > in hybrid kernel shouldn't hurt. >
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