This case however its not from the NIC FIFO, as a TCPdump running on the same interface at the same time doesn't experience the many second queuing delay.
On Jul 20, 2010, at 10:57 AM, Giorgio Calarco wrote: > hi all, > > having bursts of packets and increased jitter does not only depends on > the Click itself, but also from the queueing at the NIC FIFO. The PCI > bus is indeed fair (in the sense that it serves each peripheral > with a token passing policy), but once the peripheral acquires > access onto the bus, it's not time-limited in any way. If the bus > occupancy probability is high, for any reason, the NICs tend to accumulate > packets in their internal FIFO and once they can start the DMA > transfer, they move all the packets back-to-back, generating > a burst. I 'm not sure if this is your case (which hardware are you using ? > could the bus possibly be close to saturation ?), > anyway, you can find more details in one of the second (?) chapther > of my past PhD > thesis (it's published on the Click site - Publications). > Hope it can help in some way. > > Ciao, Giorgio > > On Tue, Jul 20, 2010 at 6:55 PM, <[email protected]> wrote: >> On 5:25 pm 07/19/10 <[email protected]> wrote: >>> I am seeing similar behavior on Linux as well. In my case, I carry some >> >> Just wanted to state that the behavior on Linux is similar but not as bad >> as Nick is reporting for OSX. I get about 20ms worth of extra jitter by >> using the To/FromDevice compared to sending the data via the RawSocket. >> >>> data between two PCs which run user-level click. If I use RawSocket >>> element, I get much better performance compared to using To/FromDevice >>> and manually composing the frames. >>> >>> >>> On 10:42 am 07/19/10 Nicholas Weaver <[email protected]> wrote: >>>> The test configuration: >>>> >>>> FromDevice(en0, PROMISC true) -> CheckIPHeader(14) -> >>>> IPPrint('reply') -> Discard; >>>> >>>> >>>> A TCPdump running at the same time gets all the packets as they are >>>> received, but the click configuration gets them in bursts (but the >>>> timestamps are right) >>>> >>>> On Jul 19, 2010, at 10:38 AM, Nicholas Weaver wrote: >>>> >>>>> I remember having a similar problem before and I don't remember what >>>>> the solution is... >>>>> On OS-X (latest version, latest devtools), FromDevice is buffering >>>>> up a large number of packets rather than receiving them in real >>>>> time. A TCPdump running at the same time does not have this problem. >>>>> >>>>> >>>>> Suggestions? >>>>> >>>>> >>>>> >>>> >>>> >>>> _______________________________________________ >>>> click mailing list >>>> [email protected] >>>> https://amsterdam.lcs.mit.edu/mailman/listinfo/click >>> >>> _______________________________________________ >>> click mailing list >>> [email protected] >>> https://amsterdam.lcs.mit.edu/mailman/listinfo/click >> >> _______________________________________________ >> click mailing list >> [email protected] >> https://amsterdam.lcs.mit.edu/mailman/listinfo/click >> > > _______________________________________________ > click mailing list > [email protected] > https://amsterdam.lcs.mit.edu/mailman/listinfo/click > _______________________________________________ click mailing list [email protected] https://amsterdam.lcs.mit.edu/mailman/listinfo/click
