[dpdk-stable] [PATCH] mem: fix allocation failure on non-NUMA kernel

[Nicolas Dichtel]

Le 05/08/2020 à 16:20, Nick Connolly a écrit :
[snip]
>>> Fixes: 2a96c88be83e ("mem: ease init in a docker container")
>> I'm wondering if the bug existed before this commit.
>>
>> Before this commit, it was:
>>         move_pages(getpid(), 1, &addr, NULL, &cur_socket_id, 0);
>>         if (cur_socket_id != socket_id) {
>>                 /* error */
>>
>> Isn't it possible to hit this error case if CONFIG_NUMA is unset in the kernel?
> I've just run the previous code to test this out and you are right that
> move_pages does indeed return -1 with errno set to ENOSYS, but nothing checks
> this so execution carries on and compares cur_socket_id (which will be unchanged
> from the zero initialization) with socket_id (which is presumably also zero),
> thus allowing the allocation to succeed!
I came to this conclusion, but I didn't check if socket_id could be != from 0.

>> [snip]
>>> +    if (check_numa()) {
>>> +        ret = get_mempolicy(&cur_socket_id, NULL, 0, addr,
>>> +                    MPOL_F_NODE | MPOL_F_ADDR);
>>> +        if (ret < 0) {
>>> +            RTE_LOG(DEBUG, EAL, "%s(): get_mempolicy: %s\n",
>>> +                __func__, strerror(errno));
>>> +            goto mapped;
>>> +        } else if (cur_socket_id != socket_id) {
>>> +            RTE_LOG(DEBUG, EAL,
>>> +                    "%s(): allocation happened on wrong socket (wanted %d,
>>> got %d)\n",
>>> +                __func__, socket_id, cur_socket_id);
>>> +            goto mapped;
>>> +        }
>>> +    } else {
>>> +        if (rte_socket_count() > 1)
>>> +            RTE_LOG(DEBUG, EAL, "%s(): not checking socket for allocation
>>> (wanted %d)\n",
>>> +                    __func__, socket_id);
>> nit: maybe an higher log level like WARNING?
> Open to guidance here - my concern was that this is going to be generated for
> every call to alloc_seg() and I'm not sure what the frequency will be - I'm
> cautious about flooding the log with warnings under 'normal running'.  Are the
> implications of running on a multi socket system with NUMA support disabled in
> the kernel purely performance related for the DPDK or is there a functional
> correctness issue as well?
Is it really a 'normal running' to have CONFIG_RTE_EAL_NUMA_AWARE_HUGEPAGES in
dpdk and not CONFIG_NUMA in the kernel?


Regards,
Nicolas