Port-xen archive

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Old Index]

Re: PV drivers in HVM DomU

On 9/28/2011 4:53 AM, Jean-Yves Migeon wrote:
For mono-CPU work, I don't think you will see much difference between
HVM and PV, except for I/O (PV should clearly win). For multi-CPU number
crunching stuff, things will be different (although this depends on the
situation): sometimes, the mono-CPU job is _faster_ that the two-CPUs
one. Lock overhead and contention, maybe.

Up to date results would be interesting. Thanks in advance if you have

Here are the results of my totally unscientific experiment...

Machine: dual Xeon 5148 2.33GHz
PV gets 2048MB RAM and 1 core
HVM gets 2048MB RAM and 4 cores (but emulated I/O)

* DL'd the 5.1 syssrc.tgz and config'd GENERIC

* created test.sh that contained nothing but "make depend && make"

* Ran "time test.sh" in PV, got the following:

>       439.94 real       318.11 user       117.53 sys

* Ran "make clean; make cleandir"

* Ran "time test.sh" in HVM, got the following:

>       638.56 real       385.82 user       226.97 sys

* Ran "make clean; make cleandir"

* Changed "make" to "make -j4" in test.sh

* Ran "time test.sh" in HVM again, got the following:

>      269.94 real        439.90 user       326.49 sys

So, it appears that the emulated I/O is significantly slower as expected, but for this job on my system, that isn't the bottleneck.


Home | Main Index | Thread Index | Old Index