pflogd eats 100% cpu now, updated -current from Feb-4 to Mar-4

Robert Watson rwatson at
Fri Mar 6 01:25:41 PST 2009

On Fri, 6 Mar 2009, Wilkinson, Alex wrote:

>    0n Thu, Mar 05, 2009 at 05:06:39PM -0600, Christian Peron wrote:
>    >We recently turned on zerocopy so it can see some exposure. I will
>    >look into this.
> Can anyone explain what this actually means ?
>  net.bpf.zerocopy_enable: Enable new zero-copy BPF buffer sessions

BPF now supports a shared memory buffering scheme between userspace and 
kernel; when the sysctl is enabled, newly opened /dev/bpf devices will permit 
configuration of the zero-copy scheme.  The sysctl doesn't turn zero-copy on 
and off per se, since existing configured sessions will continue to use it, 
but no new zero-copy sessions will be permitted when the sysctl is disabled.

However, it sounds like there's some interaction between pflogd and the 
zero-copy code that requires some debugging...

Robert N M Watson
Computer Laboratory
University of Cambridge

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