On Sun 05-05-19 14:40:57, Yafang Shao wrote:
> If CONFIG_TRANSPARENT_HUGEPAGE is not set, hpage_nr_pages() is always 1;
> if CONFIG_TRANSPARENT_HUGEPAGE is set, hpage_nr_pages() will
> call PageTransHuge() to judge whether the page is compound page or not.
> So we can use the result of hpage_nr_pages() to avoid uneccessary
> PageTransHuge().
The changelog doesn't describe motivation. Does this result in a better
code/performance?
> Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
> ---
> mm/memcontrol.c | 13 ++++++-------
> 1 file changed, 6 insertions(+), 7 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 2535e54..65c6f7c 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -6306,7 +6306,6 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage)
> {
> struct mem_cgroup *memcg;
> unsigned int nr_pages;
> - bool compound;
> unsigned long flags;
>
> VM_BUG_ON_PAGE(!PageLocked(oldpage), oldpage);
> @@ -6328,8 +6327,7 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage)
> return;
>
> /* Force-charge the new page. The old one will be freed soon */
> - compound = PageTransHuge(newpage);
> - nr_pages = compound ? hpage_nr_pages(newpage) : 1;
> + nr_pages = hpage_nr_pages(newpage);
>
> page_counter_charge(&memcg->memory, nr_pages);
> if (do_memsw_account())
> @@ -6339,7 +6337,7 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage)
> commit_charge(newpage, memcg, false);
>
> local_irq_save(flags);
> - mem_cgroup_charge_statistics(memcg, newpage, compound, nr_pages);
> + mem_cgroup_charge_statistics(memcg, newpage, nr_pages > 1, nr_pages);
> memcg_check_events(memcg, newpage);
> local_irq_restore(flags);
> }
> @@ -6533,6 +6531,7 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
> struct mem_cgroup *memcg, *swap_memcg;
> unsigned int nr_entries;
> unsigned short oldid;
> + bool compound;
>
> VM_BUG_ON_PAGE(PageLRU(page), page);
> VM_BUG_ON_PAGE(page_count(page), page);
> @@ -6553,8 +6552,9 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
> */
> swap_memcg = mem_cgroup_id_get_online(memcg);
> nr_entries = hpage_nr_pages(page);
> + compound = nr_entries > 1;
> /* Get references for the tail pages, too */
> - if (nr_entries > 1)
> + if (compound)
> mem_cgroup_id_get_many(swap_memcg, nr_entries - 1);
> oldid = swap_cgroup_record(entry, mem_cgroup_id(swap_memcg),
> nr_entries);
> @@ -6579,8 +6579,7 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
> * only synchronisation we have for updating the per-CPU variables.
> */
> VM_BUG_ON(!irqs_disabled());
> - mem_cgroup_charge_statistics(memcg, page, PageTransHuge(page),
> - -nr_entries);
> + mem_cgroup_charge_statistics(memcg, page, compound, -nr_entries);
> memcg_check_events(memcg, page);
>
> if (!mem_cgroup_is_root(memcg))
> --
> 1.8.3.1
--
Michal Hocko
SUSE Labs
