Date: Wed, 22 Jan 2014 16:23:32 -0800 From: Navdeep Parhar <np@FreeBSD.org> To: Garrett Wollman <wollman@freebsd.org>, net@freebsd.org Subject: Re: Use of contiguous physical memory in cxgbe driver Message-ID: <52E06104.70600@FreeBSD.org> In-Reply-To: <21216.22944.314697.179039@hergotha.csail.mit.edu> References: <21216.22944.314697.179039@hergotha.csail.mit.edu>
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On 01/22/14 15:52, Garrett Wollman wrote: > At this point everyone is well aware that requiring contiguous > physical page when the hardware can do scatter-gather is a very bad > idea. I wouldn't put it this way. Using buffers with size > PAGE_SIZE has its advantages. > I have a new server under test (running 9.2) which uses Chelsio > rather than Intel 10G Ethernet controllers. We fixed the Intel driver > not to use more-than-page-sized jumbo mbufs. Can anyone say with > certainty whether the Chelsio hardware actually requires > physically-contiguous allocations for jumbo frames? No it doesn't. It will do a scatter DMA if the next available rx buffer's size is less than the size of the incoming frame. > Has this already > been fixed in a more recent driver? (The hardware is identified > specifically as a T420-CR.) I'm not sure there's anything to fix here but I can add a knob that would limit the driver to a maximum of PAGE_SIZE sized rx buffers. Regards, Navdeep
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