Date: Fri, 27 Dec 2002 12:53:23 +0100 (CET) From: Harti Brandt <brandt@fokus.gmd.de> To: sparc@freebsd.org Subject: busdma on sparc Message-ID: <20021227121312.I56345-100000@beagle.fokus.gmd.de>
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Hi, I have a problem with porting my driver for the Marconi HE ATM card to sparc: The driver may (dependend on its cofiguration) need to give a lot of mbufs and mbuf clusters to the card for its different receive queues. In the biggest configuration I tried on i386 I have around 2000 clusters and 4000 mbufs. In iommu.c each dmamap eats up 32k of virtual address space (16k because of the page size and 16k for alignment). This means, that each mbuf of lesser than 200 bytes eats 32k of virtual DMA address space. This makes it impossible to allocate enough buffers to the card for high performance applications. I was under the impression, that mbufs are already aligned to every possible alignment requirements, so wouldn't it be possible to reduce the 32k to 16k on request from the driver (perhaps via one of the BUS_DMA_BUS[1-4] flags? harti -- harti brandt, http://www.fokus.gmd.de/research/cc/cats/employees/hartmut.brandt/private brandt@fokus.gmd.de, brandt@fokus.fhg.de To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-sparc" in the body of the message
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