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