On 29-Jan-21 1:45 PM, Bruce Richardson wrote:
On Fri, Jan 29, 2021 at 12:52:50PM +0000, Burakov, Anatoly wrote:
On 29-Jan-21 10:05 AM, Bruce Richardson wrote:
On Thu, Jan 28, 2021 at 04:07:07AM +0000, Oscar Zhao wrote:
Hello dpdk devs,
I would like to discuss the feasibility of implementing CPU topology detection
on FreeBSD. Currently both eal_cpu_core_id() and eal_cpu_socket_id() in rte_eal
library always return 0 on FreeBSD, making NUMA-aware development impossible
without resorting to external libraries or system APIs.
The CPU topology information is available via sysct kern.sched.topology_spec.
The only issue is that the return value is an XML formatted object (see
https://forums.freebsd.org/threads/number-of-cpus-and-cores.41299/).
(https://forums.freebsd.org/threads/number-of-cpus-and-cores.41299/) I'm not
sure how feasible it is to parse XML inside DPDK.
On a side note, obtaining the physical NUMA node id of a core is easy - sysctl
dev.cpu.[cpu#].%domain returns the corresponding node id but I have yet found a
straightforward way to detect hyperthreads besides the XML thing.
Oscar
Even adding in the numa node information would be a welcome start.
There's little value in it though, because as far as i'm aware we can't
allocate memory on specific NUMA nodes in FreeBSD.
That is because the NUMA support in FreeBSD was not in place when we first
did the DPDK port. However, I still see no reason not to start adding it
now, even if it is only for information purposes at this point.
A lot of DPDK apps will fail to work in this case, because most of them
will allocate with an explicit NUMA node. So, if you have a NUMA node
assigned to an lcore but can only allocate from NUMA node 0, any
allocation explicitly targeting NUMA node 1 will not succeed.
--
Thanks,
Anatoly
