On 01/12/2021 19:13, Oleg Ginzburg wrote:
Hi
On Wed, Dec 1, 2021 at 7:52 PM Miroslav Lachman <000.f...@quip.cz> wrote:
I was playing with VMs in VirtualBox and Bhyve and compared
performance with increasing vCPU count. The more cores VM get the slower
How many physical cores you have on the host? This is a characteristic
behavior when overcoming.
But without overcommit I observe productivity growth:
I tested it on 2 machines. One had 6 cores 12 threads, the second 4
cores 8 threads. Even if the host machine was almost idle, only one VM
was running the slowness with more than 1 vCPU was so significant. Let's
say 0.01 sec for 1 vCPU, 0.3 s for 2 vCPU, 0.9 s for 4 vCPU. (on machine
with real 4 cores / 8 threads).
With overcommit of vCPUs it was like 3 seconds with 6 vCPU and 8 seconds
for 8 vCPU. Still the same task on the same idle machine.
On the other hand I can start 5 VMs with 2 vCPUs each and "everything
seems normal" even if the total count of vCPUs are 10 on machine with 4
physical / 8 threads.
In fact I tested with total count of 15 vCPUs distributed between 5+ VMs
but the performance problem was always visible on VM with more than 2 vCPU.
1)
Single vCore benchmark via cpuminer: https://pastebin.com/mg46RvDT
TOP from host: https://pastebin.com/LvbBiyFz
2)
Sixteen vCore benchmark via cpuminer: https://pastebin.com/7FQjaVM8
TOP from host: https://pastebin.com/dLpreq9D
I observe almost linear growth.
In addition, the loss of performance can be associated with NUMA
(required cpuset/cpuset_setaffinity
and control of memory capacity)
As far as I remember, it is not enough to simply change one parameter
in .h file: https://bhyvecon.org/bhyveconOttawa2019-Rodney.pdf
Thank you for your data!
Kind regards
Miroslav Lachman
