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From: Robert Watson <rwatson@FreeBSD.org>
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Subject: PERFORCE change 137397 for review
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http://perforce.freebsd.org/chv.cgi?CH=137397

Change 137397 by rwatson@rwatson_cinnamon on 2008/03/11 14:30:41

	A bit more detail on the shared memory model and a pointer to
	bpf(4).

Affected files ...

.. //depot/projects/zcopybpf/src/sys/net/bpf_zerocopy.c#29 edit

Differences ...

==== //depot/projects/zcopybpf/src/sys/net/bpf_zerocopy.c#29 (text+ko) ====

@@ -60,7 +60,11 @@
  * are mapped into the kernel address space using sf_bufs and used directly
  * by BPF.  Memory is wired since page faults cannot be tolerated in the
  * contexts where the buffers are copied to (locks held, interrupt context,
- * etc).
+ * etc).  Access to shared memory buffers is synchronized using a header on
+ * each buffer, allowing the number of system calls to go to zero as BPF
+ * reaches saturation (buffers filled as fast as they can be drained by the
+ * user process).  Full details of the protocol for communicating between the
+ * user process and BPF may be found in bpf(4).
  */
 
 /*