[RFC] eal: allow worker lcore stacks to be allocated from hugepage memory

[Don Wallwork]

On 4/26/2022 5:21 PM, Stephen Hemminger wrote:
> On Tue, 26 Apr 2022 17:01:18 -0400
> Don Wallwork <donw at xsightlabs.com> wrote:
>
>> On 4/26/2022 10:58 AM, Stephen Hemminger wrote:
>>> On Tue, 26 Apr 2022 08:19:59 -0400
>>> Don Wallwork <donw at xsightlabs.com> wrote:
>>>   
>>>> Add support for using hugepages for worker lcore stack memory.  The
>>>> intent is to improve performance by reducing stack memory related TLB
>>>> misses and also by using memory local to the NUMA node of each lcore.
>>>>
>>>> Platforms desiring to make use of this capability must enable the
>>>> associated option flag and stack size settings in platform config
>>>> files.
>>>> ---
>>>>    lib/eal/linux/eal.c | 39 +++++++++++++++++++++++++++++++++++++++
>>>>    1 file changed, 39 insertions(+)
>>>>   
>>> Good idea but having a fixed size stack makes writing complex application
>>> more difficult. Plus you lose the safety of guard pages.
>> Thanks for the quick reply.
>>
>> The expectation is that use of this optional feature would be limited to
>> cases where
>> the performance gains justify the implications of these tradeoffs. For
>> example, a specific
>> data plane application may be okay with limited stack size and could be
>> tested to ensure
>> stack usage remains within limits.
>>
>> Also, since this applies only to worker threads, the main thread would
>> not be impacted
>> by this change.
>>
>>
> I would prefer it as a runtime, not compile time option.
> That way distributions could ship DPDK and application could opt in if it wanted.
Good point..  I'll work on a v2 and will post that when it's ready.