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SubjectRe: [PATCH] mm/migration: Add trace events for THP migrations
On Tue, Jan 11, 2022 at 10:31:21AM +0530, Anshuman Khandual wrote:
>
>
> On 1/11/22 7:28 AM, Naoya Horiguchi wrote:
> > Hi Anshuman,
> >
> > On Fri, Jan 07, 2022 at 10:29:35AM +0530, Anshuman Khandual wrote:
> >> This adds two trace events for PMD based THP migration without split. These
> >> events closely follow the implementation details like setting and removing
> >> of PMD migration entries, which are essential operations for THP migration.
> >
> > I often want to check which individual pages are migrated to which places
> > (or not migrated) for testing, so these new tracepoints could help me.
> > Maybe these can be much greater if they can handle other types of page
> > migration for raw pages and hugetlb pages. Is it hard to cover all such
> > page migration events?
>
> Are you suggesting to cover all migration entry transitions for normal
> and HugeTLB pages as well ?

Yes if you like the idea. I think that some events listed below can be grouped
into one tracepoint event with showing args like pgsize or read/write flags
(or implementation detail is up to you).

>
> migrate_pages()
> unmap_and_move_huge_page()
> try_to_migrate()
> make_writable_migration_entry() <---
> make_readable_migration_entry() <---
> remove_migration_ptes() <---
> unmap_and_move()
> __unmap_and_move()
> try_to_migrate()
> make_writable_migration_entry() <---
> make_readable_migration_entry() <---
> remove_migration_ptes() <---

Thanks,
Naoya Horiguchi

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