Hi Guys,
I'm doing my development on kind of a cheap machine with no NUMA support...
but several years ago I used DPDK to build a NUMA box that could do 40 gbits
bidirectional L4-L7 stateful traffic replay.
So given the past experiences I had before, I wanted to clean the code up so
it'd work well if some crazy guy tried my code on one of these huge boxes,
too, but then I ran into some weird issues.
1) When I call rte_eth_dev_socket_id() I get back -1. But the call can return
-1 if the port_id is bogus or if pci_scan_one didn't get a numa_node (because
you're on a non-NUMA box for example).
int rte_eth_dev_socket_id(uint8_t port_id)
{
if (port_id >= nb_ports)
return -1;
return rte_eth_devices[port_id].pci_dev->numa_node;
}
So you couldn't tell the different between non-NUMA or a bad port value, etc.
2) The code's behavior and comments disagree with one another. In the
pci_scan_one function, there's this code:
/* get numa node */
snprintf(filename, sizeof(filename), "%s/numa_node",
dirname);
if (access(filename, R_OK) != 0) {
/* if no NUMA support just set node to 0 */
dev->numa_node = -1;
} else {
if (eal_parse_sysfs_value(filename, &tmp) < 0) {
free(dev);
return -1;
}
dev->numa_node = tmp;
}
It says, just use NUMA node 0 if there is no NUMA support. But then proceeds
to set the value to -1 in disagreement with the comment, and also stomping on
the other meaning for -1 in the higher function rte_eth_dev_socket_id.
3) In conclusion, it seems like some stuff is missing... first there needs to
be a function that will tell you the number of NUMA nodes present on the box
so you can create the right number of mbuf_pools, but I couldn't find that
function.
Then if you have the function, you can do some magic and shuffle the NICs
around to get them hooked to a core on the same NUMA, and the mbuf_pool on the
same NUMA.
When NUMA is not present, can we return 0 instead of -1, or return a specific
error code that the client can use to know he should just use Socket 0? Right
now I can't tell apart any potential errors or weird values from correct
values.
4) I'm willing to help make and test some patches... but first I want to
understand what is happening with these funny functions before doing things
blindly.
Thanks,
Matthew.
