Proposed 6.2 em RELEASE patch

Mike Tancsa mike at
Fri Nov 10 22:21:13 UTC 2006

At 05:00 PM 11/10/2006, Jack Vogel wrote:
>On 11/10/06, Mike Tancsa <mike at> wrote:
>>Some more tests. I tried again with what was committed to today's
>>RELENG_6. I am guessing its pretty well the same patch.  Polling is
>>the only way to avoid livelock at a high pps rate.  Does anyone know
>>of any simple tools to measure end to end packet loss ? Polling will
>>end up dropping some packets and I want to be able to compare.  Same
>>hardware from the previous post.
>The commit WAS the last patch I posted. SO, making sure I understood you,
>you are saying that POLLING is doing better than FAST_INTR, or only
>better than the legacy code that went in with my merge?

The last set of tests I posted are ONLY with what is in today's 
RELENG_6-- i.e. the latest commit. I did a few variations on the 
driver-- first with
#define EM_FAST_INTR 1
in if_em.c

one without

and one with polling in the kernel.

With a decent packet rate passing through, the box will lockup.  Not 
sure if I am just hitting the limits of the PCIe bus, or interrupt 
moderation is not kicking in, or this is a case of "Doctor, it hurts 
when I send a lot of packets through"... "Well, dont do that"

Using polling prevents the lockup, but it will of course drop 
packets. This is for firewalls with a fairly high bandwidth rate, as 
well as I need it to be able to survive a decent DDoS attack.  I am 
not looking for 1Mpps, but something more than 100Kpps


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