Re: [PATCH v1 0/2] mm: migrate: vm event counter for hugepage migration

[Michal Hocko <mhocko@kernel.org>]

On Wed 11-04-18 17:09:25, Naoya Horiguchi wrote:
> Hi everyone,
> 
> I wrote patches introducing separate vm event counters for hugepage migration
> (both for hugetlb and thp.)
> Hugepage migration is different from normal page migration in event frequency
> and/or how likely it succeeds, so maintaining statistics for them in mixed
> counters might not be helpful both for develors and users.

This is quite a lot of code to be added se we should better document
what it is intended for. Sure I understand your reasonaning about huge
pages are more likely to fail but is this really worth a separate
counter? Do you have an example of how this would be useful?

If we are there then what about different huge page sizes (for hugetlb)?
Do we need per-hstate stats?

In other words, is this really worth it?

>  include/linux/vm_event_item.h |   7 +++
>  mm/migrate.c                  | 103 +++++++++++++++++++++++++++++++++++-------
>  mm/vmstat.c                   |   8 ++++
>  3 files changed, 102 insertions(+), 16 deletions(-)

-- 
Michal Hocko
SUSE Labs