Hi Robert, I wonder if your observed weirdness with LinkUnqueue was due to the 100%-CPU-on-DelayUnqueue problem recently reported. Maybe if you tried the configuration now?
Eddie Robert Ross wrote: > I'm not sure what this means, but we have been able to completely avoid > this problem by using kernel-level Click with the experimental > FromUserDevice, and a user-level click reading FromDump and pushing > packets out on a custom ToRawFile element. > > I will gladly put together and test a simple configuration. It would be > identical to the configuration I had attached except for switching the > Socket() to a FromDump(). I will run some more tests and send you the > monitor.csv output from our script elements. > > BTW, we used the monitor.csv output file in tandem with the Java-based > LiveGraph to see real-time statistics on Click performance. You can > also use Livegraph after the fact to open up and view our Monitor.csv > file on your end once I send you output. It has been a very nice > marriage of capabilities for real-time analysis with minimal coding. > We've done something similar in kernel-level, but had to write a custom > java application to output the monitor.csv since kernel configurations > cannot output directly to files. > > > Robert Ross > DSCI Inc. > Office: 732.542.3113 x173 > Home: 609.702.8114 > Cell: 609.509.5139 > Fax: 253.550.6198 > > -----Original Message----- > From: Eddie Kohler [mailto:[EMAIL PROTECTED] > Sent: Tuesday, January 29, 2008 2:39 PM > To: Robert Ross > Cc: Beyers Cronje; click@amsterdam.lcs.mit.edu > Subject: Re: [Click] Userlevel performance issues > > Hi Robert, > > The *job* of LinkUnqueue is specifically to throttle performance. It is > designed to output packets at the bandwidth specified. This will cause > a lower rate, pinned to that bandwidth! > > The numbers you report are kind of reasonable. Click parses bandwidths > as powers of 10, which is the networking standard as far as I can tell. > So 512Kbps = 512000bps = 64000Bps; 190p/s at this rate implies 336B > packets. So 1360p/s, for your highest bandwidth LinkUnqueue, assuming > the same packet length, is roughly half what it "should" be. That's not > great, but it's not terrible. > > I have not run your configuration with Sockets, but I have with > InfiniteSources, and so forth, and have observed LinkUnqueue outputing > packets at the correct rate. In fact I checked in an update to Counter, > to give it bit_rate and byte_rate handlers, making this easier to see. > > LinkUnqueue should affect the upstream Socket elements only indirectly. > LinkUnqueue stops pulling from its input when the emulated link is full. > This will cause an upstream Queue to fill up. Some elements might > notice that Queue's full state and stop producing packets (since those > packets will only be dropped). The InfiniteSource and user-level > FromHost elements have this behavior. However, your use of > NotifierQueue (instead of Queue) would neutralize this effect, since > NotifierQueue doesn't provide full notification. > > I am unsure in the end whether you are observing a bug or correct > behavior. > Here are a couple questions to help us figure it out. > > - Re: FromDump and ToDevice. Can you reduce the configuration as much > as possible, and tell us what rates ToDevice achieves without FromDump, > and what it achieves with FromDump? Your mail isn't specific about the > configuration or the performance numbers. > > - Re: LinkUnqueue. Can you send the output of your configuration (cool > use of define and Script btw), as well as the configuration? Again, > with InfiniteSource I see expected behavior, and I would not expect > LinkUnqueue to throttle Socket. > > It may be that you are finding an unfortunate interaction between > Click's task handlers and its file descriptor handlers -- something we > could potentially fix. But without specific numbers it's hard to tell. > > Eddie > > > Robert Ross wrote: >> The only clear item that seems to have a marked difference is the >> LinkUnqueue element. The fact that our ToDevice and FromDevice/Socket > >> performance appears to be related somehow to the configuration of a >> LinkUnqueue element sitting in the middle of our configuration is too >> obvious to ignore. Does LinkUnqueue perform some kind of >> upstream/downstream notification to these elements, causing them to >> throttle their behavior based on LinkUnqueue? >> >> In our tests, with all other elements remaining the same, here is what > >> we found from two independent read handler counts: >> >> LinkUnqueue("512Kbps") = Maximum ~190 packets/second pushed from the >> Socket element and pulled by the ToDevice element >> LinkUnqueue("1Mbps") = Maxmum ~290 packets/second pushed from the >> Socket element and pulled by the ToDevice element >> LinkUnqueue("2Mbps") = Maximum ~490 packets/second pushed from the >> Socket element and pulled by the ToDevice element >> LinkUnqueue("4Mbps") = Maximum ~780 packets/second pushed from the >> Socket element and pulled by the ToDevice element >> LinkUnqueue("6Mbps") = Maximum ~980 packets/second pushed from the >> Socket element and pulled by the ToDevice element >> LinkUnqueue("8Mbps") = Maximum ~1360 packets/second pushed from the >> Socket element and pulled by the ToDevice element >> >> It is also telling that independant handler counters corroborate >> exactly the same maximum packets per second in two very different >> places in the configuration. Clearly you can see that the limitation >> on processing is completely artificial and not an actual performance >> problem, since increasing LinkUnqueue increases the performance in a >> very controlled and obvious manner. >> >> I have attached a simple configuration that examines specific handlers > >> and outputs values each second to a CSV file for analysis. The >> configuration is scaled back to complete simplicity, yet has the same >> performance as our actual configuration which has a much more >> complicated configuration. Nevertheless, the performance is identical > >> and seems to point squarely at LinkUnqueue. >> >> What is LinkUnqueue doing that could be causing this type of effect on > >> FromHost, Socket and ToDevice? >> >> >> ________________________________ >> >> From: Robert Ross >> Sent: Friday, January 25, 2008 7:40 PM >> To: 'Beyers Cronje' >> Cc: [EMAIL PROTECTED] >> Subject: RE: [Click] Userlevel performance issues >> >> >> Sorry, I wasn't clear that the queues are necessary for our >> configuration. The configuration is somewhat complex. I was only >> attempting to highlight the important parts. >> >> >> >> >> ________________________________ >> >> From: Beyers Cronje [mailto:[EMAIL PROTECTED] >> Sent: Friday, January 25, 2008 7:31 PM >> To: Robert Ross >> Cc: [EMAIL PROTECTED] >> Subject: Re: [Click] Userlevel performance issues >> >> >> Hi Robert, >> >> >> >> >> * We first found that when UserLevel Click started pulling >> from a >> PCAP file, the performance of the ToDevice() appeared to drop >> sharply. >> What I mean by this is that the ToDevice() pull handler reported > >> values >> in the range of 200 packets/second once the PCAP file started >> reading. >> This resulted in the outbound queue just prior to the ToDevice() > >> filling >> up and eventually overflowing because the packet rate in the > PCAP >> file >> is far more than 200 packets/second. >> >> >> You dont have to use a queue between FromDump and ToDevice as FromDump > >> is an agnostic element. In other words you can connect Todevice >> directly to FromDump which should ensure that at least no packets are >> dropped and you should see best ToDevice performance. >> >> Also there are a few tuning parameters. Try tuning your NIC TX Ring >> size. On the e1000 driver the default TX ring size is 256, experiment >> with different value to see if it makes a difference.ToDevice uses a >> packet socket from transmit, so it might be worth experimenting with >> /proc/sys/net/core/wmem_default /proc/sys/net/core/wmem_max >> >> >> Beyers >> >> >> >> ---------------------------------------------------------------------- >> -- >> >> _______________________________________________ >> click mailing list >> click@amsterdam.lcs.mit.edu >> https://amsterdam.lcs.mit.edu/mailman/listinfo/click _______________________________________________ click mailing list click@amsterdam.lcs.mit.edu https://amsterdam.lcs.mit.edu/mailman/listinfo/click
