Slawa,
I'm afraid this may be a bit of a non-sequitur. Sorry.. I seem to be
missing something. As I understand it this thread is about Ryan's change
to netinet for broadcast.
On 26/08/16 15:49, Slawa Olhovchenkov wrote:
On Sun, Aug 21, 2016 at 03:04:00AM +0300, Slawa Olhovchenkov wrote:
On Sun, Aug 21, 2016 at 12:25:46AM +0100, Bruce Simpson wrote:
Whilst I agree with your concerns about multipoint, I support the
motivation behind Ryan's original change: optimize the common case.
Oh, common case...
I am have pmc profiling for TCP output and see on this SVG picture and
don't find any simple way.
You want to watch too?
At time peak network traffic (more then 25K connections, about 20Gbit
total traffic) half of cores fully utilised by network stack.
This is flamegraph from one core: http://zxy.spb.ru/cpu10.svg
This is same, but stack cut of at ixgbe_rxeof for more unified
tcp/ip stack view http://zxy.spb.ru/cpu10u.svg
...
I appreciate that you've taken the time to post a flamegraph (a
fashionable visualization) of relative performance in the FreeBSD
networking stack.
Sadly, I am mostly out of my depth for looking at stack wide performance
for the moment; for the things I look at involving FreeBSD at work just
at the moment, I would not generally go down there except for specific
performance issues (e.g. with IEEE 1588).
It sounds as though perhaps you should raise a wider discussion about
your results on -net. I would caution you however that the Function
Boundary Trace (FBT) provider for DTrace can introduce a fair amount of
noise to the raw performance data because of the trap mechanism it uses.
This ruled it out for one of my own studies requiring packet-level accuracy.
Whilst raw pmc(4) profiles may require more post-processing, they will
provide less equivocal data (and a better fix) on the hot path, due also
to being sampled effectively on a PMC interrupt (a gather stage- poll
core+uncore MSRs), not purely a software timer interrupt.
thanks
Bruce
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