|Summary:||Full-duplex Gigabit can not reach gigabit at both RX/TX same time|
|Product:||Red Hat Enterprise Linux 3||Reporter:||Robinson Tiemuqinke <hahaha_30k>|
|Component:||kernel||Assignee:||John W. Linville <linville>|
|Status:||CLOSED WONTFIX||QA Contact:||Brian Brock <bbrock>|
|Fixed In Version:||Doc Type:||Bug Fix|
|Doc Text:||Story Points:||---|
|Last Closed:||2005-08-03 16:11:22 UTC||Type:||---|
|oVirt Team:||---||RHEL 7.3 requirements from Atomic Host:|
|Cloudforms Team:||---||Target Upstream Version:|
Description Robinson Tiemuqinke 2005-06-10 01:33:33 UTC
Description of problem: Full-duplex mode Gigabit can not reach near gigabit at both sending and receiving sides. Instead, the sum of sending and receiving reaches gigabit. The tests are ttcp tests on two HP workstation XW4200. Case 1, only receiving, no sending. The sending speed is near 0MBytes/s, receiving speed is 110MB/s. case 2, only sending, no receiving. The sending speed is near 110MB/s, receiving speed is near 0MB/s. case 3, both sending and receiving at the same time. The sending speed is about 55MB/s, receiving at about 55MB/s. Version-Release number of selected component (if applicable): How reproducible: Every time. Not only on Redhat Enterprise Linux, but also on Fedora Core series. Steps to Reproduce: 1. Install Redhat Enterprise 3 or 4 onto two HP Workstation XW4200, or similar machines with high PCI Bus speed. and connect the builtin Broadcom network cards with a crossover CAT6 cable. This way exclues the LAN Switch factor. 2. run ttcp on the two machines, either as sending role, or as receiving role. 3.test all the 3 cases in the "Description of Problem" section. and the results will be quite similar. Actual results: Expected results: When machines' gigabit(in full-duplex gigabit mode) in sending and receiving data at the same time, both the sending speed and receiving speed should be around 110MB/s. And the SUM of them should be 220MB/s. Additional info: According to HP support technician, the HP workstation XW4200 has a PCI EXpress bus which support 2.5GB/s data transfer. "top" commands reports that machine box still have 80% Idle CPU cycles.
Comment 1 Ernie Petrides 2005-06-10 04:20:27 UTC
*** Bug 160020 has been marked as a duplicate of this bug. ***
Comment 2 David Miller 2005-06-10 05:26:28 UTC
Not true, the some should not be 220MB/sec. You're forgetting that the opposite direction of the transfer is consumed by ACK packets. So for the single transfer case you have: SENDER --> DATA --> DATA --> DATA --> DATA --> DATA --> RECEIVER SENDER <-- ACK <-- ACK <-- ACK <-- ACK <-- ACK <-- RECEIVER With the case of two transfers going at once you have: Host1 --> DATA --> ACK --> DATA --> ACK --> DATA --> ACK Host2 Host2 <-- ACK <-- DATA <-- ACK <-- DATA <-- ACK <-- DATA Host2 This is not a bug.
Comment 3 Robinson Tiemuqinke 2005-06-10 17:42:21 UTC
David Miller, Thanks for you quick reply. But I've also tested the normal 100Mbits/s network cards in full-duplex modes. with two pairs of sending-receiving ttcp on two Redhat Linux hosts. The results are: On each machine, the sending side speed is 12MB/s, receiving speed is also at 12MB/s. totally the SUM is 24MB/s, quite close to the capacity of 200Mbits/s(added sending and receiving sides). The above is quite easy to reproduce, you can use two 100Mbits/s cards, or Gigabit works at 100Mbits/s fFull-duplex mode. The OS can be Redhat Enterprise Linux or Fedora Core, kernel can be 2.4 or 2.6. The results is exactly the same.
Comment 4 John W. Linville 2005-06-10 18:08:24 UTC
What NICs are you using (particular in the xw4200)? Are they actually PCI-E? Or are they PCI(-X)? Please attach the output of running "sysreport" to this bug. Thanks!
Comment 5 John W. Linville 2005-08-03 16:11:22 UTC
Closed due to inactivity. Please reopen when requested information becomes available. Thanks!