[Xen-devel] Lower bandwidth with TSO?

[Jae-Wan Jang <jwjang@xxxxxxxxxxxxxxxxxx>]

Hello,

I have measured bandwidth between domU guest os and normal Linux
which are connected using direct cable.
Pentium D 930 (dual core) is used for Xen and Pentium 4 3.0Ghz is
used for the Linux box.
Also broadcom BCM5701 PCI-based gigabit Ethernet card is attached
to Pentium D.

When I enable TSO in netfront, I got 624 Mbps over TCP connection.
But when I disable TSO, I got 651 Mbps.
Repeated measurements shows the similar results.

During the experiment, I see the CPU utilization using xentop.
TSO off -> 60.1/34.8 (dom0/domU)
TSO on -> 47.5/22.2 (dom0/domU)

Is it possible to get this number?
And is there any reasons for this situation?



Thanks,
Jae-Wan

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