Thanks. If interrupt mitigation disabling won't be enough I will have do decide: freebs with netmap or openbsd with if_ethersubr.c modification.
netmap looks much easier to code. No need to do the mbuf dance (or I hope that with netmap there would be no such need). BTW, would HW TX IP/UDP checksum reduce the latency? Best regards, Dan On Mon, Feb 11, 2013 at 2:11 PM, Mike Belopuhov <m...@belopuhov.com> wrote: > On 11 February 2013 12:53, Dan Shechter <dans...@gmail.com> wrote: >> Thanks, >> >> Are there any other tips to reduce latency? >> > > Using pcap means copying packets, so I'd say you want to > put your code into the kernel to avoid copying and maybe > queueing as well, but this is not something that can be > trivially explained and is certainly not something that > OpenBSD supports or would want to support out of the box. > > FreeBSD netmap interface would be helpful in your situation > but is not currently supported by OpenBSD. > > Cheers, > Mike > >> >> Best regards, >> Dan >> >> >> On Mon, Feb 11, 2013 at 1:43 PM, Mike Belopuhov <m...@belopuhov.com> wrote: >>> On 11 February 2013 12:19, Dan Shechter <dans...@gmail.com> wrote: >>>> Hi All, >>>> >>>> I have a very latency sensitive application. I need to move packets >>>> from one interface to another >>>> >>>> I am using a quad 1000/pro Intel NIC. pcidump shows 82571EB >>>> >>>> My latency sensitive application reads packets from one em interface >>>> using libpcap and sends packet to another em interface using udp >>>> socket. >>>> >>>> Does em has interrupt mitigation enabled? >>> >>> It does. >>> >>>> If interrupt mitigation is enabled would disabling it will reduce latency? >>> >>> It would. >>> >>>> How can I disable the interrupt mitigation for em NICs? >>> >>> I suggest you try increasing MAX_INTS_PER_SEC define by the factor >>> or two in /sys/dev/pci/if_em.h. In case it doesn't suite your needs you >>> can try commenting out this line: >>> >>> E1000_WRITE_REG(&sc->hw, ITR, DEFAULT_ITR); >>> >>>> What would change in 5.3? >>>> >>> >>> Nothing regarding interrupt moderation. >>> >>>> Best regards, >>>> Dan >>>> >>> >>> Cheers, >>> Mike
