limited network bandwidth with 3.2.x kernels

alekcejk
2012-02-13T20:05:07Z

Hi,

I noticed that with 3.2.x kernels download speed from some internet resources
became about half of speed that was with previous kernels (3.1 and older).
I tested Fedora 15 kernels 2.6.41.10 = 3.1.10 and 2.6.42.3 = 3.2.3
(many times rebooted for testing with first and second kernels).
See bug https://bugzilla.redhat.com/show_bug.cgi?id=789659

lsmod:
Module Size Used by
nvidia 10778232 40
i2c_core 28123 1 nvidia
8139too 32490 0
mii 13311 1 8139too

dmesg:
8139too: 8139too Fast Ethernet driver 0.9.28
8139too 0000:01:02.0: PCI INT A -> GSI 22 (level, low) -> IRQ 22
8139too 0000:01:02.0: eth0: RealTek RTL8139 at , IRQ 22
8139too 0000:01:02.0: eth0: link up, 100Mbps, full-duplex, lpa 0x41E1

For testing I selected fastest for me download mirrors of FreeBSD and Ubuntu,
also I tested download speed from site speedtest.tele2.net.

For these sites download speed with 3.1 kernels (and older) is about 11 MB/s
but with 3.2.x kernels - limited 5.5 MB/s and for some sites still approximately
the same as with 3.1 kernels (see bug mentioned above).

Also I want to pay attention that limited speed stays constant - always
5.5 MB/s with straight line on traffic plotter as if was network bandwidth shaping.
With 3.1 kernels this never happens - speed can vary in some ranges
but at maximum it is about 11 MB/s, no limitations such as 5.5 MB/s.

--
Alexey Kurov <nucleo@fedoraproject.org>