Hi Ryan,
On 2024/7/4 17:46, Ryan Roberts wrote:
On 03/07/2024 17:02, Bang Li wrote:
On 2024/7/3 18:25, Ryan Roberts wrote:
On 03/07/2024 08:33, Bang Li wrote:
Hi Ryan,
Thanks for the review!
On 2024/7/2 16:18, Ryan Roberts wrote:
On 02/07/2024 03:34, Bang Li wrote:
After the commit 7fb1b252afb5 ("mm: shmem: add mTHP support for
anonymous shmem"), we can configure different policies through
the multi-size THP sysfs interface for anonymous shmem. But
currently "THPeligible" indicates only whether the mapping is
eligible for allocating THP-pages as well as the THP is PMD
mappable or not for anonymous shmem, we need to support semantics
for mTHP with anonymous shmem similar to those for mTHP with
anonymous memory.
Signed-off-by: Bang Li <libang.li@xxxxxxxxxxxx>
---
Changes since v1 [1]:
- Put anonymous shmem mthp related logic into
thp_vma_allowable_orders() (per David)
[1]
https://lore.kernel.org/linux-mm/20240628104926.34209-1-libang.li@xxxxxxxxxxxx/
---
include/linux/huge_mm.h | 11 +++++++++++
mm/huge_memory.c | 13 +++++++++----
mm/shmem.c | 9 +--------
3 files changed, 21 insertions(+), 12 deletions(-)
diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 212cca384d7e..f87136f38aa1 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -267,6 +267,10 @@ unsigned long thp_vma_allowable_orders(struct
vm_area_struct *vma,
return __thp_vma_allowable_orders(vma, vm_flags, tva_flags, orders);
}
+unsigned long shmem_allowable_huge_orders(struct inode *inode,
+ struct vm_area_struct *vma, pgoff_t index,
+ bool global_huge);
+
struct thpsize {
struct kobject kobj;
struct list_head node;
@@ -460,6 +464,13 @@ static inline unsigned long
thp_vma_allowable_orders(struct vm_area_struct *vma,
return 0;
}
+static inline unsigned long shmem_allowable_huge_orders(struct inode
*inode,
+ struct vm_area_struct *vma, pgoff_t index,
+ bool global_huge)
+{
+ return 0;
+}
+
#define transparent_hugepage_flags 0UL
#define thp_get_unmapped_area NULL
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index c7ce28f6b7f3..ea377bb4af91 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -151,10 +151,15 @@ unsigned long __thp_vma_allowable_orders(struct
vm_area_struct *vma,
* Must be done before hugepage flags check since shmem has its
* own flags.
*/
- if (!in_pf && shmem_file(vma->vm_file))
- return shmem_is_huge(file_inode(vma->vm_file), vma->vm_pgoff,
- !enforce_sysfs, vma->vm_mm, vm_flags)
- ? orders : 0;
+ if (!in_pf && shmem_file(vma->vm_file)) {
+ bool global_huge = shmem_is_huge(file_inode(vma->vm_file),
vma->vm_pgoff,
+ !enforce_sysfs, vma->vm_mm, vm_flags);
+
+ if (!vma_is_anon_shmem(vma))
+ return global_huge? orders : 0;
nit: missing space before '?'
Yes, thanks.
+ return shmem_allowable_huge_orders(file_inode(vma->vm_file),
+ vma, vma->vm_pgoff, global_huge);
What's the rationale for splitting these functions into shmem_is_huge() and
shmem_allowable_huge_orders()? Why not just have a single
shmem_allowable_huge_orders() that tells you the answer?
Currently, shmem_is_huge() is used for all shmem implementations to determine
whether the conditions for using THP are met. And shmem_allowable_huge_orders()
is currently mainly used for anonymous shmem's mTHP to obtain all orders that
meet the conditions. In my opinion, there is no problem in separating these two
functions. In the future, when mTHP of other shmem types is also implemented,
will shmem_is_huge() be unnecessary?
Personally, I consider shmem_is_huge() to be superfluous; If you have one
function, shmem_allowable_huge_orders(), that gives you all the information you
need. If the inode only allows PMD-size, then only return that bit in the field.
IMHO removing shmem_is_huge() would make things more readable.
Thank you very much for your opinion. I think there is no big problem in keeping
the current interface status quo. In my opinion, when we implement mTHP for all
shmems, it may be better to remove shmem_is_huge() and use
shmem_allowable_huge_orders() uniformly. I believe that it won't be long before
someone proposes a non-anonymous shared mTHP patchset. Anyway, thank you for
your suggestion :).
See [1] for an expanded list of concerns I have about the current state of the
interface and implementation.
OK, could you please send me the corresponding link ;)？
Thanks，
Bang
Thanks,
Ryan
Thanks,
Bang
Thanks,
Ryan
Thanks,
Bang
+ }
if (!vma_is_anonymous(vma)) {
/*
diff --git a/mm/shmem.c b/mm/shmem.c
index d495c0701a83..aa85df9c662a 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1622,7 +1622,7 @@ static gfp_t limit_gfp_mask(gfp_t huge_gfp, gfp_t
limit_gfp)
}
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
-static unsigned long shmem_allowable_huge_orders(struct inode *inode,
+unsigned long shmem_allowable_huge_orders(struct inode *inode,
struct vm_area_struct *vma, pgoff_t index,
bool global_huge)
{
@@ -1707,13 +1707,6 @@ static unsigned long shmem_suitable_orders(struct
inode *inode, struct vm_fault
return orders;
}
#else
-static unsigned long shmem_allowable_huge_orders(struct inode *inode,
- struct vm_area_struct *vma, pgoff_t index,
- bool global_huge)
-{
- return 0;
-}
-
static unsigned long shmem_suitable_orders(struct inode *inode, struct
vm_fault *vmf,
struct address_space *mapping, pgoff_t index,
unsigned long orders)
