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

[Nick Connolly <nick.connolly@mayadata.io>]

On 05/08/2020 16:13, Nicolas Dichtel wrote:
> Le 05/08/2020 à 16:53, Nick Connolly a écrit :
> [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?
>> I'm not an expert of DPDK, but I think it needs to be treated as 'normal
>> running', for the following reasons:
>>
>> 1. The existing code in eal_memalloc_alloc_seg_bulk() is designed to
>>     work even if check_numa() indicates that NUMA support is not enabled:
>>
>>     #ifdef RTE_EAL_NUMA_AWARE_HUGEPAGES
>>     if (check_numa()) {
>>              oldmask = numa_allocate_nodemask();
>>              prepare_numa(&oldpolicy, oldmask, socket);
>>              have_numa = true;
>>          }
>>     #endif
> The question was not to return an error, but to display a warning. So the code
> will work (after your patch), no problem.
>
>> 2. The DPDK application could be built with
>>     CONFIG_RTE_EAL_NUMA_AWARE_HUGE_PAGES and then the binary run on
>>     different systems with and without NUMA support.
> In a production environment, it seems odd to have a custom kernel and a generic
> dpdk app, it's why I propose the log level WARNING (or NOTICE maybe?).
> I let other comment about this, I don't have a strong opinion.
Thanks - appreciate the input - I also have no strong opinions here and 
am happy to be guided.

Regards,
Nick