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

[David Hildenbrand]

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@xxxxxxxxxxxxx>
> > >
> > > 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