Re: [RFC PATCH 3/3] hugetlb: Lazy page table copies in fork()

[Muchun Song]

On Fri, May 27, 2022 at 03:58:49PM -0700, Mike Kravetz wrote:
> Lazy page table copying at fork time was introduced with commit
> d992895ba2b2 ("Lazy page table copies in fork()").  At the time,
> hugetlb was very new and did not support page faulting.  As a result,
> it was excluded.  When full page fault support was added for hugetlb,
> the exclusion was not removed.
> 
> Simply remove the check that prevents lazy copying of hugetlb page
> tables at fork.  Of course, like other mappings this only applies to
> shared mappings.
> 
> Lazy page table copying at fork will be less advantageous for hugetlb
> mappings because:
> - There are fewer page table entries with hugetlb
> - hugetlb pmds can be shared instead of copied
> 
> In any case, completely eliminating the copy at fork time shold speed
> things up.
> 
> Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>

Acked-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>

Thanks.