The patch titled
Subject: mm: accelerate munlock() treatment of THP pages
has been added to the -mm tree. Its filename is
mm-accelerate-munlock-treatment-of-thp-pages.patch
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------------------------------------------------------
From: Michel Lespinasse <walken@xxxxxxxxxx>
Subject: mm: accelerate munlock() treatment of THP pages
munlock_vma_pages_range() was always incrementing addresses by PAGE_SIZE
at a time. When munlocking THP pages (or the huge zero page), this
resulted in taking the mm->page_table_lock 512 times in a row.
We can do better by making use of the page_mask returned by
follow_page_mask (for the huge zero page case), or the size of the page
munlock_vma_page() operated on (for the true THP page case).
Note - I am sending this as RFC only for now as I can't currently put my
finger on what if anything prevents split_huge_page() from operating
concurrently on the same page as munlock_vma_page(), which would mess up
our NR_MLOCK statistics. Is this a latent bug or is there a subtle point
I missed here ?
Signed-off-by: Michel Lespinasse <walken@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/internal.h | 2 +-
mm/mlock.c | 34 +++++++++++++++++++++++-----------
2 files changed, 24 insertions(+), 12 deletions(-)
diff -puN mm/internal.h~mm-accelerate-munlock-treatment-of-thp-pages mm/internal.h
--- a/mm/internal.h~mm-accelerate-munlock-treatment-of-thp-pages
+++ a/mm/internal.h
@@ -195,7 +195,7 @@ static inline int mlocked_vma_newpage(st
* must be called with vma's mmap_sem held for read or write, and page locked.
*/
extern void mlock_vma_page(struct page *page);
-extern void munlock_vma_page(struct page *page);
+extern unsigned int munlock_vma_page(struct page *page);
/*
* Clear the page's PageMlocked(). This can be useful in a situation where
diff -puN mm/mlock.c~mm-accelerate-munlock-treatment-of-thp-pages mm/mlock.c
--- a/mm/mlock.c~mm-accelerate-munlock-treatment-of-thp-pages
+++ a/mm/mlock.c
@@ -102,13 +102,16 @@ void mlock_vma_page(struct page *page)
* can't isolate the page, we leave it for putback_lru_page() and vmscan
* [page_referenced()/try_to_unmap()] to deal with.
*/
-void munlock_vma_page(struct page *page)
+unsigned int munlock_vma_page(struct page *page)
{
+ unsigned int page_mask = 0;
+
BUG_ON(!PageLocked(page));
if (TestClearPageMlocked(page)) {
- mod_zone_page_state(page_zone(page), NR_MLOCK,
- -hpage_nr_pages(page));
+ unsigned int nr_pages = hpage_nr_pages(page);
+ mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages);
+ page_mask = nr_pages - 1;
if (!isolate_lru_page(page)) {
int ret = SWAP_AGAIN;
@@ -141,6 +144,8 @@ void munlock_vma_page(struct page *page)
count_vm_event(UNEVICTABLE_PGMUNLOCKED);
}
}
+
+ return page_mask;
}
/**
@@ -159,7 +164,6 @@ long __mlock_vma_pages_range(struct vm_a
unsigned long start, unsigned long end, int *nonblocking)
{
struct mm_struct *mm = vma->vm_mm;
- unsigned long addr = start;
unsigned long nr_pages = (end - start) / PAGE_SIZE;
int gup_flags;
@@ -189,7 +193,7 @@ long __mlock_vma_pages_range(struct vm_a
* We made sure addr is within a VMA, so the following will
* not result in a stack expansion that recurses back here.
*/
- return __get_user_pages(current, mm, addr, nr_pages, gup_flags,
+ return __get_user_pages(current, mm, start, nr_pages, gup_flags,
NULL, NULL, nonblocking);
}
@@ -226,13 +230,12 @@ static int __mlock_posix_error_return(lo
void munlock_vma_pages_range(struct vm_area_struct *vma,
unsigned long start, unsigned long end)
{
- unsigned long addr;
-
- lru_add_drain();
vma->vm_flags &= ~VM_LOCKED;
- for (addr = start; addr < end; addr += PAGE_SIZE) {
+ while (start < end) {
struct page *page;
+ unsigned int page_mask, page_increm;
+
/*
* Although FOLL_DUMP is intended for get_dump_page(),
* it just so happens that its special treatment of the
@@ -240,13 +243,22 @@ void munlock_vma_pages_range(struct vm_a
* suits munlock very well (and if somehow an abnormal page
* has sneaked into the range, we won't oops here: great).
*/
- page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP);
+ page = follow_page_mask(vma, start, FOLL_GET | FOLL_DUMP,
+ &page_mask);
if (page && !IS_ERR(page)) {
lock_page(page);
- munlock_vma_page(page);
+ lru_add_drain();
+ /*
+ * Any THP page found by follow_page_mask() may have
+ * gotten split before reaching munlock_vma_page(),
+ * so we need to recompute the page_mask here.
+ */
+ page_mask = munlock_vma_page(page);
unlock_page(page);
put_page(page);
}
+ page_increm = 1 + (~(start >> PAGE_SHIFT) & page_mask);
+ start += page_increm * PAGE_SIZE;
cond_resched();
}
}
_
Patches currently in -mm which might be from walken@xxxxxxxxxx are
linux-next.patch
mm-remove-free_area_cache-use-in-powerpc-architecture.patch
mm-use-vm_unmapped_area-on-powerpc-architecture.patch
mm-use-vm_unmapped_area-on-ia64-architecture.patch
mm-use-vm_unmapped_area-in-hugetlbfs-on-ia64-architecture.patch
mm-use-vm_unmapped_area-on-parisc-architecture.patch
mm-remap_file_pages-fixes.patch
mm-introduce-mm_populate-for-populating-new-vmas.patch
mm-use-mm_populate-for-blocking-remap_file_pages.patch
mm-use-mm_populate-when-adjusting-brk-with-mcl_future-in-effect.patch
mm-use-mm_populate-for-mremap-of-vm_locked-vmas.patch
mm-remove-flags-argument-to-mmap_region.patch
mm-remove-flags-argument-to-mmap_region-fix.patch
mm-directly-use-__mlock_vma_pages_range-in-find_extend_vma.patch
mm-introduce-vm_populate-flag-to-better-deal-with-racy-userspace-programs.patch
mm-make-do_mmap_pgoff-return-populate-as-a-size-in-bytes-not-as-a-bool.patch
mm-remove-free_area_cache.patch
mm-use-long-type-for-page-counts-in-mm_populate-and-get_user_pages.patch
mm-accelerate-mm_populate-treatment-of-thp-pages.patch
mm-accelerate-munlock-treatment-of-thp-pages.patch
mm-use-vm_unmapped_area-on-frv-architecture.patch
mm-use-vm_unmapped_area-on-alpha-architecture.patch
mtd-mtd_nandecctest-use-prandom_bytes-instead-of-get_random_bytes.patch
mtd-mtd_oobtest-convert-to-use-prandom-library.patch
mtd-mtd_pagetest-convert-to-use-prandom-library.patch
mtd-mtd_speedtest-use-prandom_bytes.patch
mtd-mtd_subpagetest-convert-to-use-prandom-library.patch
mtd-mtd_stresstest-use-prandom_bytes.patch
mutex-subsystem-synchro-test-module.patch
--
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