Re: [PATCH v2 2/2] hugetlb: optimize update_and_free_pages_bulk to avoid lock cycles

[Muchun Song]

> On Jul 18, 2023, at 08:49, Mike Kravetz <mike.kravetz@xxxxxxxxxx> wrote:
> 
> update_and_free_pages_bulk is designed to free a list of hugetlb pages
> back to their associated lower level allocators.  This may require
> allocating vmemmmap pages associated with each hugetlb page.  The
> hugetlb page destructor must be changed before pages are freed to lower
> level allocators.  However, the destructor must be changed under the
> hugetlb lock.  This means there is potentially one lock cycle per page.
> 
> Minimize the number of lock cycles in update_and_free_pages_bulk by:
> 1) allocating necessary vmemmap for all hugetlb pages on the list
> 2) take hugetlb lock and clear destructor for all pages on the list
> 3) free all pages on list back to low level allocators
> 
> Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>

Reviewed-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>

Thanks.