Re: [RFC] mm/vmstat: Add events for HugeTLB migration

[Oscar Salvador]

On Fri, Sep 25, 2020 at 02:42:29PM +0530, Anshuman Khandual wrote:
> Add following new vmstat events which will track HugeTLB page migration.
> 
> 1. HUGETLB_MIGRATION_SUCCESS
> 2. HUGETLB_MIGRATION_FAILURE
> 
> It follows the existing semantics to accommodate HugeTLB subpages in total
> page migration statistics. While here, this updates current trace event
> "mm_migrate_pages" to accommodate now available HugeTLB based statistics.
> 
> Cc: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx>
> Cc: Zi Yan <ziy@xxxxxxxxxx>
> Cc: John Hubbard <jhubbard@xxxxxxxxxx>
> Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: linux-mm@xxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>

Was this inspired by some usecase/debugging or just to follow THP's example?

>  	int retry = 1;
>  	int thp_retry = 1;
> +	int hugetlb_retry = 1;
>  	int nr_failed = 0;
>  	int nr_succeeded = 0;
>  	int nr_thp_succeeded = 0;
>  	int nr_thp_failed = 0;
>  	int nr_thp_split = 0;
> +	int nr_hugetlb_succeeded = 0;
> +	int nr_hugetlb_failed = 0;
>  	int pass = 0;
>  	bool is_thp = false;
> +	bool is_hugetlb = false;
>  	struct page *page;
>  	struct page *page2;
>  	int swapwrite = current->flags & PF_SWAPWRITE;
> @@ -1433,6 +1437,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
>  	for (pass = 0; pass < 10 && (retry || thp_retry); pass++) {

Should you not have put hugetlb_retry within the loop as well?
Otherwise we might not rety for hugetlb pages now?

-- 
Oscar Salvador
SUSE L3