Date: Tue, 11 Mar 2008 14:57:48 GMT From: Robert Watson <rwatson@FreeBSD.org> To: Perforce Change Reviews <perforce@freebsd.org> Subject: PERFORCE change 137403 for review Message-ID: <200803111457.m2BEvmX5042003@repoman.freebsd.org>
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http://perforce.freebsd.org/chv.cgi?CH=137403 Change 137403 by rwatson@rwatson_cinnamon on 2008/03/11 14:57:12 Update README. Affected files ... .. //depot/projects/zcopybpf/README#5 edit Differences ... ==== //depot/projects/zcopybpf/README#5 (text+ko) ==== @@ -4,12 +4,12 @@ Reduce the number of system calls, copies, and even context switches in BPF by adding shared memory buffers between userspace and the kernel. Processes select zero-copy buffer mode, "donate" two buffers to the kernel, which are -used in place of the two kernel memory buffers in BPF. They can then use -BPF ioctls to query the state of the buffers, acknowledge/rotate them, -select on their being ready to read, etc. They can also use a solely shared -memory interface to check for new data and acknowledge buffers, so as load -increases, the number of system calls required to access the BPF stream -approaches zero. +used in place of the two kernel memory buffers in BPF. The process uses a +shared memory interface to check for new data and acknowledge buffers, but +can also use an ioctl to force early rotation of a buffer before it is full +(timeout), and select()/poll()/kevent() to wait for a buffer to fill. This +API allows the number of system calls used to access BPF data to go to zero +as the load increases. This implementation was created by Robert N. M. Watson under contract to Seccuris Inc., in collaboration with Christian S. J. Peron of Seccuris Inc, @@ -19,21 +19,20 @@ -------- Untar the tarball and drop the new src/ files into your src/ tree; this -should consist of two new .c files and two new .h files in src/sys/net/, and -two sample kernel config files that enable BPF_ZEROCOPY. +should consist of two new .c files and two new .h files in src/sys/net/. Apply the patch, which should modify a number of files in the kernel, especially src/sys/net and src/sys/conf, as well as in contrib/libpcap in order to teach the pcap library how to use zero-copy buffers. -Build a fresh kernel and install it, with options BPF_ZEROCOPY if you want -zero-copy buffer support. Build and install a fresh libpcap. +Build a fresh kernel and install it; build and install a fresh libpcap. -A new sysctl will be present, net.bpf.zerocopy_enable -- if it is set to 1 -(the default) then all new BPF sessions created by libpcap will use zero-copy -support. If set to 0, new sessions will use buffered reads. The -BPF_ZERO_COPY/BPF_ZEROCOPY environmental variables used in earlier prototypes -have now been removed in favour of this model. +A new sysctl will be present, net.bpf.zerocopy_enable -- when it is set to 1 +all new BPF sessions created by libpcap will use zero-copy support. If set +to 0, new sessions will use buffered reads. The BPF_ZEROCOPY kernel option +and BPF_ZERO_COPY/BPF_ZEROCOPY environmental variables used in earlier +prototypes have now been removed in favour of this run-time configuration +model. Notes -----
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