On Thu, Dec 03, 2015 at 04:47:29PM +0100, Michal Hocko wrote:
> On Thu 03-12-15 15:58:50, Michal Hocko wrote:
> [....]
> > Warning, this looks ugly as hell.
>
> I was thinking about it some more and it seems that we should rather not
> bother with partial thp at all and keep it in the original memcg
> instead. It is way much less code and I do not think this will be too
> disruptive. Somebody should be holding the thp head, right?
>
> Minchan, does this fix the issue you are seeing.
This patch solves the issue but not sure it's right approach.
I think it could make regression that in old, we could charge
a THP page but we can't now. Whether it's trivial or not, it depends
on memcg guys.
Thanks.
> ---
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 79a29d564bff..143c933f0b81 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -4895,6 +4895,14 @@ static int mem_cgroup_move_charge_pte_range(pmd_t *pmd,
> switch (get_mctgt_type(vma, addr, ptent, &target)) {
> case MC_TARGET_PAGE:
> page = target.page;
> + /*
> + * We can have a part of the split pmd here. Moving it
> + * can be done but it would be too convoluted so simply
> + * ignore such a partial THP and keep it in original
> + * memcg. There should be somebody mapping the head.
> + */
> + if (PageCompound(page))
> + goto put;
> if (isolate_lru_page(page))
> goto put;
> if (!mem_cgroup_move_account(page, false,
> --
> Michal Hocko
> SUSE Labs
--
Kind regards,
Minchan Kim
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