Le samedi 17 décembre 2011 à 17:18 -0600, Larry Finger a écrit : > In https://bugzilla.novell.com/show_bug.cgi?id=718736, a user reports that his > network using an RTL8188CE becomes very slow under "heavy" load. This condition > started when he updated from openSUSE 11.4 to 12.1. The kernels involved are > 2.6.37 and 3.1. I am unable to duplicate the problem. > > Packet capture with Wireshark shows that the slow down is due to retransmissions > due to TCP checksum errors. I found nothing to explain the situation with a > Google search, thus I am asking here. > > I put heavy in quotes because the traffic is from a web browser to yahoo.com, > thus the potential throughput is not very high. > > As far as I know, this checksum is generated in a higher layer of the network > stack, and that data is just passed through the 802.11 layer, and the wireless > driver. Is this correct? Anyone have any ideas on where to look for the problem? > I see nothing special in the packet capture from this bug report. (Only suboptimal application opening many concurrent flows in //) Keep in mind most modern NICS compute checksums themselve. Linux offloads this to NIC This can be controled eventually by "ethtool -k ethX" (-K to change settings) # ethtool -k eth0 Offload parameters for eth0: rx-checksumming: on tx-checksumming: on scatter-gather: on tcp-segmentation-offload: on udp-fragmentation-offload: off generic-segmentation-offload: on generic-receive-offload: on large-receive-offload: off rx-vlan-offload: on tx-vlan-offload: on ntuple-filters: off receive-hashing: off # ethtool -K eth0 tx off # ethtool -k eth0 Offload parameters for eth0: rx-checksumming: on tx-checksumming: off scatter-gather: off tcp-segmentation-offload: off udp-fragmentation-offload: off generic-segmentation-offload: off generic-receive-offload: on large-receive-offload: off rx-vlan-offload: on tx-vlan-offload: on ntuple-filters: off receive-hashing: off -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
