On Tue, 20 Dec 2011 14:48:14 -0800, YongHyeon PYUN wrote:
I also see similar excessive system load with em(4) on latest HEAD.
Self-clocking protocols like TCP does not seem to suffer from the
issue but UDP clearly shows the issue. A single bulk UDP transmit
test session completely halts the box while the test is in
progress. I have a patch that addresses it but it needs more clean
ups and Jack's review. I'm not sure whether the patch could be
accepted since it completely removes taskqueue based approach in
TX/RX path.
Also note, multi-queue option of igb(4) can re-order UDP packets in
TX path such that it can result in poor NFS over UDP performance.
It seems TCP is more resilient on packet reodering though.
Because igb(4) shares implementation idea with em(4), it's possible
igb(4) also have the similar issue. I have to find some spare time
to try this with igb(4) but I'm somewhat overloaded to address poor
em(4) performance on 82574 with MSI-X.
I decided to try the updated igb driver, v2.2.5, in FreeBSD 9.0RC3. I
can no longer duplicate the excessive load issue as it now performs so
poorly that I can't even stream a 38Mbit/s file via either NFS/UDP or
Samba/TCP, so things went from bad to worse. I'm guessing it has
something to do with flow control as that's appears to be different with
this driver, back to v2.2.3 for now.
Thanks,
Clint
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