On 04/30/2013 01:36 PM, Melanie Witt wrote:
This presentation from the summit might be of interest to you:
http://www.openstack.org/summit/portland-2013/session-videos/presentation/scaling-the-boot-barrier-identifying-and-eliminating-contention-in-openstack
A nice presentation. Based on his comment at the end, I did the web
search and found his slides at:
http://www.cs.utoronto.ca/~peter/feiner_slides_openstack_summit_portland_2013.pdf
A caveat/nit/whatnot about looking at overall system CPU utilization and
assuming no CPU bottleneck (the "hardware" portion at the beginning) at
points even well below 100% utilization - with multiple CPUs in a system
now, there are for example, many ways for there to be 50% overall CPU
utilization. It could be that all the CPUs are indeed at 50% util, but
it could also be that 1/2 the CPUs are at 100% and the other half are
idle. Now, perhaps that fits in the space between a hardware and a
software bottleneck, but I'd be cautious about overall CPU utilization
figures.
For example, a single or small number of CPUs saturating can happen
rather easily in some "networking" workloads - the CPU servicing
interrupts from the NIC (or CPUs if the NIC is multiqueue) can saturate.
I'd consider that a hardware saturation, even though many of the other
CPUs in the system are largely idle. That is why in later versions of
netperf, there is a way to report the ID and utilization of the most
utilized CPU during a test, in addition to reporting the overall CPU
utilization.
rick jones
_______________________________________________
Mailing list: https://launchpad.net/~openstack
Post to : openstack@lists.launchpad.net
Unsubscribe : https://launchpad.net/~openstack
More help : https://help.launchpad.net/ListHelp
