[dpdk-dev] [PATCH] mem: fix allocation failure on non-NUMA kernel
Nick Connolly
nick.connolly at mayadata.io
Wed Aug 5 17:21:57 CEST 2020
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
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