Date: Sun, 11 Jan 2004 13:56:31 -0800 (PST) From: Don Lewis <truckman@FreeBSD.org> To: bms@spc.org Cc: richard_bejtlich@yahoo.com Subject: Re: Paper on device polling and packet capture performance Message-ID: <200401112156.i0BLuV7E031435@gw.catspoiler.org> In-Reply-To: <20040111195740.GK17555@saboteur.dek.spc.org>
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On 11 Jan, Bruce M Simpson wrote: > On Fri, Jan 09, 2004 at 03:51:43PM -0600, Guy Helmer wrote: >> I want to look at memory-mapped access to the BPF device. >> This would preserve the existing network device drivers >> while reducing mbuf copies, context switches/user-kernel >> transitions, and latency. Performance ought to be >> comparable to Luca's approach, and this would also >> preserve bpf filtering capability. >> >> (If someone else has already done this, I'd love to >> know where to find the code!) > > I did review some patches related to this last month but they weren't > for FreeBSD. One big problem with the approach involved which leapt out > at me was that the space was allocated within user address space, which > introduces the risk of page faults (as you may know we can't ever fault > with a mutex held -- or it's game over). You'd have to wire the buffer. Beyond a certain buffer size, you'd probably want to maintain a sliding window of of wired memory to avoid wiring an excessive amount of memory.
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