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PERFORCE change 114152 for review

Subject: PERFORCE change 114152 for review
From: "Christian S.J. Peron"
Date: Wed, 7 Feb 2007 05:01:31 GMT
http://perforce.freebsd.org/chv.cgi?CH=114152

Change 114152 by [email protected]_rnd01 on 2007/02/07 05:01:04

        Annotate that in the future before we issue wakesup, we might do 
something like:
        
        (1) Check to see if this descriptor is operating in immediate mode
        (2) Check to see if the holder buffer is NULL
        (3) Check to see if we are waking up any sleepers
        
        We do not need to check the store buffer, as the fact that it has data 
in it
        at this point in the code is invariant.
        
        If the following conditions are true, then rotate the buffer. This will 
save
        userspace from issuing an ioctl(2) potentially per wakeup.

Affected files ...

.. //depot/projects/zcopybpf/src/sys/net/bpf.c#14 edit

Differences ...

==== //depot/projects/zcopybpf/src/sys/net/bpf.c#14 (text+ko) ====

@@ -1760,6 +1760,11 @@
        (*cpfn)(d, d->bd_sbuf, curlen + hdrlen, pkt, hdr.bh_caplen);
        d->bd_slen = curlen + totlen;
 
+       /*
+        * XXXCSJP we could probably save a syscall per wakeup if we check the
+        * d->bd_immediate flag, hold buffer status and rotate the buffers
+        * before the wakeup.
+        */
        if (do_wakeup)
                bpf_wakeup(d);
 }
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