Date: Wed, 6 Feb 2013 17:20:50 +0200 From: Jacques Fourie <jacques.fourie@gmail.com> To: John Baldwin <jhb@freebsd.org> Cc: Hackers freeBSD <freebsd-hackers@freebsd.org>, Axel Fischer <afischer@marvell.com>, Lino Sanfilippo <lsanfil@marvell.com>, Markus Althoff <malthoff@marvell.com> Subject: Re: Mbuf memory handling Message-ID: <CALX0vxADMfWe1-_mOYnx0C-9cRxf-ETv6wOPn=%2B34NATNUbbKA@mail.gmail.com> In-Reply-To: <201302060836.55404.jhb@freebsd.org> References: <175CCF5F49938B4D99B2E3EF7F558EBE1C73F401F3@SC-VEXCH4.marvell.com> <201302060836.55404.jhb@freebsd.org>
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On Wed, Feb 6, 2013 at 3:36 PM, John Baldwin <jhb@freebsd.org> wrote: > On Wednesday, February 06, 2013 4:50:39 am Lino Sanfilippo wrote: > > > > Hi all, > > > > I want to implement a device driver for a NIC which stores received data > into chunks within > > a page (>=4k) in host memory. One page shall be used for multiple > packets and freed > > after all mbufs linked to that page have been processed. So I would like > to know what is the recommended way > > to handle this in FreeBSD? Any hints are very appreciated. > > I think you can get what you want by allocating M_JUMBOP mbuf clusters for > your receive buffers. When you want to split out a packet, allocate a new > packet header mbuf and use m_split() to let it take over the rest of the 4k > buffer and pass the original mbuf up to if_input() as the new packet. The > new mbufs you attach to the cluster via m_split() will all hold a reference > on the backing cluster and it won't be freed until all the mbufs are freed. > > The resulting mbufs will not be writeable (M_WRITABLE() will evaluate to 0), right? I don't know if this will be an issue in this particular application. > -- > John Baldwin > _______________________________________________ > freebsd-hackers@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-hackers > To unsubscribe, send any mail to "freebsd-hackers-unsubscribe@freebsd.org" >
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