Date: Wed, 27 Aug 2003 11:40:17 -0500 (CDT) From: Mike Silbersack <silby@silby.com> To: "Giovanni P. Tirloni" <gpt@tirloni.org> Cc: freebsd-net@freebsd.org Subject: Re: mbuf usage for an idle machine Message-ID: <20030827113639.A4269@odysseus.silby.com> In-Reply-To: <20030827030314.GJ40033@pixies.tirloni.org> References: <20030827030314.GJ40033@pixies.tirloni.org>
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On Wed, 27 Aug 2003, Giovanni P. Tirloni wrote: > Hi, > > I've been reading about mbufs and how they're used for > holding network packets and socket buffers and the > output of 'netstat -m' for a idle machine I've here > made me curious about how FreeBSD handles it in -CURRENT. > > Why is it using so many mbufs when it's idle? My > small kwnowledge doesn't permit me to answer this > question yet ;) The mbufs in question are (mostly) being used as receive buffers by the network drivers. With modern DMA based cards, you pre-allocate the buffers, then hand them over to the card's control. Once they're filled with packet data, the NIC informs the OS, which replaces them with new buffers. A lot of our drivers have 128 (or some power of 2) receive buffers, hence your mbuf usage. Mike "Silby" Silbersack
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