Bugzilla – Bug 2330
default device queue size for PointToPointNetDevice
Last modified: 2016-11-24 15:23:48 EST
Created attachment 2334 [details] suggested patch Now that we have traffic control integrated with PointToPointNetDevice, it seems that we should consider to shrink the default queue size on the device. It presently is at 100 packets (ns3::Queue default). The following patch shrinks it to 3 (which is default for Linux PPP). Only one test suite fails due to this proposed change: List of FAILed tests: adaptive-red-queue-disc Documentation would need to be updated with this behavioral change.
(In reply to Tom Henderson from comment #0) > Now that we have traffic control integrated with PointToPointNetDevice, it > seems that we should consider to shrink the default queue size on the > device. It presently is at 100 packets (ns3::Queue default). The following > patch shrinks it to 3 (which is default for Linux PPP). Agreed. Also because some preliminary tests we are doing with our preliminary implementation of BQL show that BQL keeps the device queue size at 3 packets on average. Also, a device queue of 100 packets basically makes AQM algorithms useless. Regarding the patch: I assume you set the maximum number of bytes because the user might switch the queue mode to bytes and hence you need to set such a limit. Just a question: why did you use 65535? If the user leaves the default mtu, this means that the device queue can store (3 * 65535) / 1500 ~= 130 packets. > Only one test suite fails due to this proposed change: > List of FAILed tests: > adaptive-red-queue-disc This test fails because of some magic numbers hardcoded in the test. I contacted Mohit because modifying the flow control mechanism (as part of the latest requeue rework) also made this test fail. Mohit is working on fixing this.
(In reply to Stefano Avallone from comment #1) > Regarding the patch: I assume you set the maximum number of bytes because > the user might switch the queue mode to bytes and hence you need to set such > a limit. Just a question: why did you use 65535? If the user leaves the > default mtu, this means that the device queue can store (3 * 65535) / 1500 > ~= 130 packets. IMHO we can check the MTU to set the bytes amount, i.e. (3 * GetMtu ()). Also, instead of raw number 3, we can use a constant uint declared in the class.
Created attachment 2685 [details] suggested patch r1 incorporating Natale's suggestions
(In reply to Tom Henderson from comment #3) > Created attachment 2685 [details] > suggested patch r1 > > incorporating Natale's suggestions it would be a good time to resolve bug 1604 so we can more easily access the default MTU, so I marked as a dependency.