This change adds a follow_page_mask function which is equivalent to
follow_page, but with an extra page_mask argument.
follow_page_mask sets *page_mask to HPAGE_PMD_NR - 1 when it encounters a
THP page, and to 0 in other cases.
__get_user_pages() makes use of this in order to accelerate populating
THP ranges - that is, when both the pages and vmas arrays are NULL,
we don't need to iterate HPAGE_PMD_NR times to cover a single THP page
(and we also avoid taking mm->page_table_lock that many times).
Signed-off-by: Michel Lespinasse <wal...@google.com>
---
include/linux/mm.h | 13 +++++++++++--
mm/memory.c | 31 +++++++++++++++++++++++--------
mm/nommu.c | 6 ++++--
3 files changed, 38 insertions(+), 12 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 3d9fbcf9fa94..31e4d42002ee 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1636,8 +1636,17 @@ int vm_insert_pfn(struct vm_area_struct *vma, unsigned
long addr,
int vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
unsigned long pfn);
-struct page *follow_page(struct vm_area_struct *, unsigned long address,
- unsigned int foll_flags);
+struct page *follow_page_mask(struct vm_area_struct *vma,
+ unsigned long address, unsigned int foll_flags,
+ unsigned int *page_mask);
+
+static inline struct page *follow_page(struct vm_area_struct *vma,
+ unsigned long address, unsigned int foll_flags)
+{
+ unsigned int unused_page_mask;
+ return follow_page_mask(vma, address, foll_flags, &unused_page_mask);
+}
+
#define FOLL_WRITE 0x01 /* check pte is writable */
#define FOLL_TOUCH 0x02 /* mark page accessed */
#define FOLL_GET 0x04 /* do get_page on page */
diff --git a/mm/memory.c b/mm/memory.c
index f0b6b2b798c4..52c8599e7fe4 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1458,10 +1458,11 @@ int zap_vma_ptes(struct vm_area_struct *vma, unsigned
long address,
EXPORT_SYMBOL_GPL(zap_vma_ptes);
/**
- * follow_page - look up a page descriptor from a user-virtual address
+ * follow_page_mask - look up a page descriptor from a user-virtual address
* @vma: vm_area_struct mapping @address
* @address: virtual address to look up
* @flags: flags modifying lookup behaviour
+ * @page_mask: on output, *page_mask is set according to the size of the page
*
* @flags can have FOLL_ flags set, defined in <linux/mm.h>
*
@@ -1469,8 +1470,9 @@ EXPORT_SYMBOL_GPL(zap_vma_ptes);
* an error pointer if there is a mapping to something not represented
* by a page descriptor (see also vm_normal_page()).
*/
-struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
- unsigned int flags)
+struct page *follow_page_mask(struct vm_area_struct *vma,
+ unsigned long address, unsigned int flags,
+ unsigned int *page_mask)
{
pgd_t *pgd;
pud_t *pud;
@@ -1480,6 +1482,8 @@ struct page *follow_page(struct vm_area_struct *vma,
unsigned long address,
struct page *page;
struct mm_struct *mm = vma->vm_mm;
+ *page_mask = 0;
+
page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
if (!IS_ERR(page)) {
BUG_ON(flags & FOLL_GET);
@@ -1526,6 +1530,7 @@ struct page *follow_page(struct vm_area_struct *vma,
unsigned long address,
page = follow_trans_huge_pmd(vma, address,
pmd, flags);
spin_unlock(&mm->page_table_lock);
+ *page_mask = HPAGE_PMD_NR - 1;
goto out;
}
} else
@@ -1680,6 +1685,7 @@ long __get_user_pages(struct task_struct *tsk, struct
mm_struct *mm,
{
long i;
unsigned long vm_flags;
+ unsigned int page_mask;
if (!nr_pages)
return 0;
@@ -1757,6 +1763,7 @@ long __get_user_pages(struct task_struct *tsk, struct
mm_struct *mm,
get_page(page);
}
pte_unmap(pte);
+ page_mask = 0;
goto next_page;
}
@@ -1774,6 +1781,7 @@ long __get_user_pages(struct task_struct *tsk, struct
mm_struct *mm,
do {
struct page *page;
unsigned int foll_flags = gup_flags;
+ unsigned int page_increm;
/*
* If we have a pending SIGKILL, don't keep faulting
@@ -1783,7 +1791,8 @@ long __get_user_pages(struct task_struct *tsk, struct
mm_struct *mm,
return i ? i : -ERESTARTSYS;
cond_resched();
- while (!(page = follow_page(vma, start, foll_flags))) {
+ while (!(page = follow_page_mask(vma, start,
+ foll_flags, &page_mask))) {
int ret;
unsigned int fault_flags = 0;
@@ -1857,13 +1866,19 @@ long __get_user_pages(struct task_struct *tsk, struct
mm_struct *mm,
flush_anon_page(vma, page, start);
flush_dcache_page(page);
+ page_mask = 0;
}
next_page:
- if (vmas)
+ if (vmas) {
vmas[i] = vma;
- i++;
- start += PAGE_SIZE;
- nr_pages--;
+ page_mask = 0;
+ }
+ page_increm = 1 + (~(start >> PAGE_SHIFT) & page_mask);
+ if (page_increm > nr_pages)
+ page_increm = nr_pages;
+ i += page_increm;
+ start += page_increm * PAGE_SIZE;
+ nr_pages -= page_increm;
} while (nr_pages && start < vma->vm_end);
} while (nr_pages);
return i;
diff --git a/mm/nommu.c b/mm/nommu.c
index 429a3d5217fa..9a6a25181267 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -1817,9 +1817,11 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned
long, old_len,
return ret;
}
-struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
- unsigned int foll_flags)
+struct page *follow_page_mask(struct vm_area_struct *vma,
+ unsigned long address, unsigned int flags,
+ unsigned int *page_mask)
{
+ *page_mask = 0;
return NULL;
}
--
1.8.1
--
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