[-next,v2,09/19] mm: mprotect: use a folio in change_pte_range()
Commit Message
Use a folio in change_pte_range() to save three compound_head() calls.
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
---
mm/mprotect.c | 16 +++++++++-------
1 file changed, 9 insertions(+), 7 deletions(-)
Comments
On Fri, Oct 13, 2023 at 04:55:53PM +0800, Kefeng Wang wrote:
> Use a folio in change_pte_range() to save three compound_head() calls.
Yes, but here we have a change of behaviour, which should be argued
is desirable. Before if a partial THP was mapped, or a fs large
folio, we would do this to individual pages. Now we're doing it to the
entire folio. Is that desirable? I don't have the background to argue
either way.
> @@ -157,7 +159,7 @@ static long change_pte_range(struct mmu_gather *tlb,
> continue;
> if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING &&
> !toptier)
> - xchg_page_access_time(page,
> + folio_xchg_access_time(folio,
> jiffies_to_msecs(jiffies));
> }
On 2023/10/13 23:13, Matthew Wilcox wrote:
> On Fri, Oct 13, 2023 at 04:55:53PM +0800, Kefeng Wang wrote:
>> Use a folio in change_pte_range() to save three compound_head() calls.
>
> Yes, but here we have a change of behaviour, which should be argued
> is desirable. Before if a partial THP was mapped, or a fs large
> folio, we would do this to individual pages. Now we're doing it to the
> entire folio. Is that desirable? I don't have the background to argue
> either way.
The Huang's replay in v1[1] already mentioned this, we only use
last_cpupid from head page, and large folio won't be handled from
do_numa_page(), and if large folio numa balancing is supported,
we could migrate the entire large folio mapped only one process,
or maybe split the large folio mapped multi-processes, and when
split it, we will copy the last_cpupid from head to the tail page.
Anyway, I think this change or the wp_page_reuse() won't break
current numa balancing.
Thanks.
[1]https://lore.kernel.org/linux-mm/874jixhfeu.fsf@yhuang6-desk2.ccr.corp.intel.com/
>
>> @@ -157,7 +159,7 @@ static long change_pte_range(struct mmu_gather *tlb,
>> continue;
>> if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING &&
>> !toptier)
>> - xchg_page_access_time(page,
>> + folio_xchg_access_time(folio,
>> jiffies_to_msecs(jiffies));
>> }
>
@@ -114,7 +114,7 @@ static long change_pte_range(struct mmu_gather *tlb,
* pages. See similar comment in change_huge_pmd.
*/
if (prot_numa) {
- struct page *page;
+ struct folio *folio;
int nid;
bool toptier;
@@ -122,13 +122,14 @@ static long change_pte_range(struct mmu_gather *tlb,
if (pte_protnone(oldpte))
continue;
- page = vm_normal_page(vma, addr, oldpte);
- if (!page || is_zone_device_page(page) || PageKsm(page))
+ folio = vm_normal_folio(vma, addr, oldpte);
+ if (!folio || folio_is_zone_device(folio) ||
+ folio_test_ksm(folio))
continue;
/* Also skip shared copy-on-write pages */
if (is_cow_mapping(vma->vm_flags) &&
- page_count(page) != 1)
+ folio_ref_count(folio) != 1)
continue;
/*
@@ -136,14 +137,15 @@ static long change_pte_range(struct mmu_gather *tlb,
* it cannot move them all from MIGRATE_ASYNC
* context.
*/
- if (page_is_file_lru(page) && PageDirty(page))
+ if (folio_is_file_lru(folio) &&
+ folio_test_dirty(folio))
continue;
/*
* Don't mess with PTEs if page is already on the node
* a single-threaded process is running on.
*/
- nid = page_to_nid(page);
+ nid = folio_nid(folio);
if (target_node == nid)
continue;
toptier = node_is_toptier(nid);
@@ -157,7 +159,7 @@ static long change_pte_range(struct mmu_gather *tlb,
continue;
if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING &&
!toptier)
- xchg_page_access_time(page,
+ folio_xchg_access_time(folio,
jiffies_to_msecs(jiffies));
}