[...] >>> ixgbe_main.c. All you are doing with this patch is denying the user >>> choice with this change as they then are not allowed to set more >> >> Yes, it is purposed to deny configuration that doesn't benefit. > > Doesn't benefit who? It is obvious you don't understand how DCB is > meant to work since you are assuming the queues are throw-away. > Anyone who makes use of the ability to prioritize their traffic would > likely have a different opinion.
+1 this is actually needed so that when DCB is turned on we can see both prioritize between tcs (DCB feature) but also do not see a performance degradation with just a single TC transmitting. If we break this (and its happened occasionally) we end up with bug reports so its clear to me folks care about it. > >>> queues. Even if they find your decision was wrong for their >>> configuration. >>> >>> - Alex >>> >> Thanks, >> Ethan > > Your response clearly points out you don't understand DCB. I suggest > you take another look at how things are actually being configured. I > believe what you will find is that the current implementation is > basing things on the number of online CPUs already based on the > ring_feature[RING_F_RSS].limit value. All that is happening is that > you are getting that value multiplied by the number of TCs and the RSS > value is reduced if the result is greater than 64 based on the maximum > number of queues. > > With your code on an 8 core system you go from being able to perform > RSS over 8 queues to only being able to perform RSS over 1 queue when > you enable DCB. There was a bug a long time ago where this actually > didn't provide any gain because the interrupt allocation was binding > all 8 RSS queues to a single q_vector, but that has long since been > fixed and what you should be seeing is that RSS will spread traffic > across either 8 or 16 queues when DCB is enabled in either 8 or 4 TC > mode. > > My advice would be to use a netperf TCP_CRR test and watch what queues > and what interrupts traffic is being delivered to. Then if you have > DCB enabled on both ends you might try changing the priority of your > netperf session and watch what happens when you switch between TCs. > What you should find is that you will shift between groups of queues > and as you do so you should not have any active queues overlapping > unless you have less interrupts than CPUs. > Yep. Thanks, John > - Alex > _______________________________________________ > Intel-wired-lan mailing list > intel-wired-...@lists.osuosl.org > http://lists.osuosl.org/mailman/listinfo/intel-wired-lan >
