bcopy's performance on 2.4.20 (Redhat) and 2.40.20-8um (UML)

From: firnnauriel
Date: Thu Dec 16 2004 - 01:47:05 EST

Greetings to all! I would like to ask for your advice
regarding this question:
"In general, is the memcpy"s performance on UML (User
Mode Linux) environment better than the host OS? If
that is the case, can you give the reason behind it
(ex. UML"s architecture)?"

Here"s the evironment:
OS: Redhat 9 (kernel 2.4.20-8)
Brand/Model: Dell PowerEdge 2600
CPU: Intel Xeon 2.4 GHz
Memory: 2 GB
Disk Space: 73 GB

Kernel version : 2.40.20-lsm1-8um
Allocated Mem : 256MB

I used lmbench-2.0.4 for the bandwith and latency
testing. here"s the result:

memcpy : 597.1 MB/s (higher is better)
page fault : 2.00000 (smaller is better)

memcpy : 668.4
page fault : 48.0

The result in page fault might be because of low
memory allocated in UML. But the question is, why is
the memcpy on UML (668.4 MB/s) performs faster that
the host OS?

I already asked the developer of lmbench, and he
adviced me to ask this question to the linux kernel
mailing list.

I would really appreciate any inputs and advice.

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