Bug 215535

Summary: The network speed from xen0 to HVM guest is slow
Product: Red Hat Enterprise Linux 5 Reporter: Chris Lalancette <clalance>
Component: kernelAssignee: Herbert Xu <herbert.xu>
Status: CLOSED NOTABUG QA Contact: Brian Brock <bbrock>
Severity: medium Docs Contact:
Priority: medium    
Version: 5.0CC: tao, xen-maint
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Hardware: All   
OS: Linux   
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Last Closed: 2007-05-23 22:47:47 UTC Type: ---
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description Chris Lalancette 2006-11-14 15:56:49 UTC
Description of problem:
From Intel:
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In the testing for RHEL5 Beta2 M5 we found that the network speed from xen0 to
hvm guest is very slow.
The highest speed is 1.8MB/s and the lowest is 20KB/s, the average is 200KB/s.
And Guest==>Xen0 is about 2MB/s, it's also slow .
In unstable tree, the speed should be at least more than 5MB/s.
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They also reproduced on M9.  In my own testing on i386, I saw nothing of the
sort; I saw ~7MB/s from dom0 to domU, and ~4MB/s from domU to dom0.  So this may
be hardware dependent.

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Comment 1 Herbert Xu 2006-11-14 20:14:20 UTC
Is this with qemu? If so please try again with the PV netfront driver.  qemu
drivers are known to be slow due the high emulation overhead.

Comment 3 Herbert Xu 2006-11-30 03:01:09 UTC
The PV driver isn't currently part of the baremetal RHEL5 kernel.

Yes you can build it for RHEL5 without rebuilding the entire kernel.

While SMP and 32/64 support may indeed be lacking at this point in time, they're
being addressed upstream.  On the other hand, there really isn't much that can
be done to bring qemu performance to the level of PV performance.

Comment 4 Herbert Xu 2006-11-30 03:03:09 UTC
For all practical purposes, if you care about performance you should be using a
PV kernel with RHEL5.