Re: [RFC PATCH v1 0/4] hugetlb: parallelize hugetlb page allocation on boot

David Hildenbrand
2023-11-24T19:47:53Z

On 24.11.23 20:44, David Rientjes wrote:
> On Thu, 23 Nov 2023, David Hildenbrand wrote:
>
>> On 23.11.23 14:30, Gang Li wrote:
>>> From: Gang Li <ligang.bdlg@bytedance.com>
>>>
>>> Inspired by these patches [1][2], this series aims to speed up the
>>> initialization of hugetlb during the boot process through
>>> parallelization.
>>>
>>> It is particularly effective in large systems. On a machine equipped
>>> with 1TB of memory and two NUMA nodes, the time for hugetlb
>>> initialization was reduced from 2 seconds to 1 second.
>>
>> Sorry to say, but why is that a scenario worth adding complexity for /
>> optimizing for? You don't cover that, so there is a clear lack in the
>> motivation.
>>
>> 2 vs. 1 second on a 1 TiB system is usually really just noise.
>>
>
> The cost will continue to grow over time, so I presume that Gang is trying
> to get out in front of the issue even though it may not be a large savings
> today.
>
> Running single boot tests, with the latest upstream kernel, allocating
> 1,440 1GB hugetlb pages on a 1.5TB AMD host appears to take 1.47s.
>
> But allocating 11,776 1GB hugetlb pages on a 12TB Intel host takes 65.2s
> today with the current implementation.

And there, the 65.2s won't be noise because that 12TB system is up by a
snap of a finger? :)

--
Cheers,

David / dhildenb