The patch titled
Subject: mm: always enable thp for dax mappings
has been added to the -mm tree. Its filename is
mm-always-enable-thp-for-dax-mappings.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-always-enable-thp-for-dax-mappings.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-always-enable-thp-for-dax-mappings.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Dan Williams <dan.j.williams@xxxxxxxxx>
Subject: mm: always enable thp for dax mappings
The madvise policy for transparent huge pages is meant to avoid unwanted
allocations of transparent huge pages. It allows a policy of disabling
the extra memory pressure and effort to arrange for a huge page when it is
not needed.
DAX by definition never incurs this overhead since it is statically
allocated. The policy choice makes even less sense for device-dax which
tries to guarantee a given tlb-fault size. Specifically, the following
setting:
echo never > /sys/kernel/mm/transparent_hugepage/enabled
...violates that guarantee and silently disables all device-dax instances
with a 2M or 1G alignment. So, let's avoid that non-obvious side effect
by force enabling thp for dax mappings in all cases.
It is worth noting that the reason this uses vma_is_dax(), and the
resulting header include changes, is that previous attempts to add a
VM_DAX flag were NAKd.
Link: http://lkml.kernel.org/r/149739531127.20686.15813586620597484283.stgit@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Reviewed-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/dax.h | 5 -----
include/linux/fs.h | 6 ++++++
include/linux/huge_mm.h | 5 +++++
3 files changed, 11 insertions(+), 5 deletions(-)
diff -puN include/linux/dax.h~mm-always-enable-thp-for-dax-mappings include/linux/dax.h
--- a/include/linux/dax.h~mm-always-enable-thp-for-dax-mappings
+++ a/include/linux/dax.h
@@ -142,11 +142,6 @@ static inline unsigned int dax_radix_ord
#endif
int dax_pfn_mkwrite(struct vm_fault *vmf);
-static inline bool vma_is_dax(struct vm_area_struct *vma)
-{
- return vma->vm_file && IS_DAX(vma->vm_file->f_mapping->host);
-}
-
static inline bool dax_mapping(struct address_space *mapping)
{
return mapping->host && IS_DAX(mapping->host);
diff -puN include/linux/fs.h~mm-always-enable-thp-for-dax-mappings include/linux/fs.h
--- a/include/linux/fs.h~mm-always-enable-thp-for-dax-mappings
+++ a/include/linux/fs.h
@@ -18,6 +18,7 @@
#include <linux/bug.h>
#include <linux/mutex.h>
#include <linux/rwsem.h>
+#include <linux/mm_types.h>
#include <linux/capability.h>
#include <linux/semaphore.h>
#include <linux/fiemap.h>
@@ -3048,6 +3049,11 @@ static inline bool io_is_direct(struct f
return (filp->f_flags & O_DIRECT) || IS_DAX(filp->f_mapping->host);
}
+static inline bool vma_is_dax(struct vm_area_struct *vma)
+{
+ return vma->vm_file && IS_DAX(vma->vm_file->f_mapping->host);
+}
+
static inline int iocb_flags(struct file *file)
{
int res = 0;
diff -puN include/linux/huge_mm.h~mm-always-enable-thp-for-dax-mappings include/linux/huge_mm.h
--- a/include/linux/huge_mm.h~mm-always-enable-thp-for-dax-mappings
+++ a/include/linux/huge_mm.h
@@ -1,6 +1,8 @@
#ifndef _LINUX_HUGE_MM_H
#define _LINUX_HUGE_MM_H
+#include <linux/fs.h> /* only for vma_is_dax() */
+
extern int do_huge_pmd_anonymous_page(struct vm_fault *vmf);
extern int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
@@ -101,6 +103,9 @@ static inline bool transparent_hugepage_
if (transparent_hugepage_flags & (1 << TRANSPARENT_HUGEPAGE_FLAG))
return true;
+ if (vma_is_dax(vma))
+ return true;
+
if (transparent_hugepage_flags &
(1 << TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG))
return !!(vma->vm_flags & VM_HUGEPAGE);
_
Patches currently in -mm which might be from dan.j.williams@xxxxxxxxx are
mm-improve-readability-of-transparent_hugepage_enabled.patch
mm-always-enable-thp-for-dax-mappings.patch
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
