* mm: ptl is not bloated if it fits in pointer
@ 2013-12-16 9:04 ` Hugh Dickins
0 siblings, 0 replies; 10+ messages in thread
From: Hugh Dickins @ 2013-12-16 9:04 UTC (permalink / raw)
To: Kirill A. Shutemov
Cc: Peter Zijlstra, Linus Torvalds, Andrew Morton, linux-kernel, linux-mm
It's silly to force the 64-bit CONFIG_GENERIC_LOCKBREAK architectures
to kmalloc eight bytes for an indirect page table lock: the lock needs
to fit in the space that a pointer to it would occupy, not into an int.
Signed-off-by: Hugh Dickins <hughd@google.com>
---
kernel/bounds.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- 3.13-rc4/kernel/bounds.c 2013-11-22 15:40:37.452192638 -0800
+++ linux/kernel/bounds.c 2013-12-15 14:34:36.304485959 -0800
@@ -22,6 +22,6 @@ void foo(void)
#ifdef CONFIG_SMP
DEFINE(NR_CPUS_BITS, ilog2(CONFIG_NR_CPUS));
#endif
- DEFINE(BLOATED_SPINLOCKS, sizeof(spinlock_t) > sizeof(int));
+ DEFINE(BLOATED_SPINLOCKS, sizeof(spinlock_t) > sizeof(spinlock_t *));
/* End of constants */
}
^ permalink raw reply [flat|nested] 10+ messages in thread
* mm: ptl is not bloated if it fits in pointer
@ 2013-12-16 9:04 ` Hugh Dickins
0 siblings, 0 replies; 10+ messages in thread
From: Hugh Dickins @ 2013-12-16 9:04 UTC (permalink / raw)
To: Kirill A. Shutemov
Cc: Peter Zijlstra, Linus Torvalds, Andrew Morton, linux-kernel, linux-mm
It's silly to force the 64-bit CONFIG_GENERIC_LOCKBREAK architectures
to kmalloc eight bytes for an indirect page table lock: the lock needs
to fit in the space that a pointer to it would occupy, not into an int.
Signed-off-by: Hugh Dickins <hughd@google.com>
---
kernel/bounds.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- 3.13-rc4/kernel/bounds.c 2013-11-22 15:40:37.452192638 -0800
+++ linux/kernel/bounds.c 2013-12-15 14:34:36.304485959 -0800
@@ -22,6 +22,6 @@ void foo(void)
#ifdef CONFIG_SMP
DEFINE(NR_CPUS_BITS, ilog2(CONFIG_NR_CPUS));
#endif
- DEFINE(BLOATED_SPINLOCKS, sizeof(spinlock_t) > sizeof(int));
+ DEFINE(BLOATED_SPINLOCKS, sizeof(spinlock_t) > sizeof(spinlock_t *));
/* End of constants */
}
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
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see: http://www.linux-mm.org/ .
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^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: mm: ptl is not bloated if it fits in pointer
2013-12-16 9:04 ` Hugh Dickins
@ 2013-12-16 10:04 ` Peter Zijlstra
-1 siblings, 0 replies; 10+ messages in thread
From: Peter Zijlstra @ 2013-12-16 10:04 UTC (permalink / raw)
To: Hugh Dickins
Cc: Kirill A. Shutemov, Linus Torvalds, Andrew Morton, linux-kernel,
linux-mm
On Mon, Dec 16, 2013 at 01:04:13AM -0800, Hugh Dickins wrote:
> It's silly to force the 64-bit CONFIG_GENERIC_LOCKBREAK architectures
> to kmalloc eight bytes for an indirect page table lock: the lock needs
> to fit in the space that a pointer to it would occupy, not into an int.
Ah, no. A spinlock is very much assumed to be 32bit, any spinlock that's
bigger than that is bloated.
For the page-frame case we do indeed not care about the strict 32bit but
more about not being larger than a pointer, however there are already
other users.
See for instance include/linux/lockref.h and lib/lockref.c, they very
much require the spinlock to be 32bit and the below would break that.
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: mm: ptl is not bloated if it fits in pointer
@ 2013-12-16 10:04 ` Peter Zijlstra
0 siblings, 0 replies; 10+ messages in thread
From: Peter Zijlstra @ 2013-12-16 10:04 UTC (permalink / raw)
To: Hugh Dickins
Cc: Kirill A. Shutemov, Linus Torvalds, Andrew Morton, linux-kernel,
linux-mm
On Mon, Dec 16, 2013 at 01:04:13AM -0800, Hugh Dickins wrote:
> It's silly to force the 64-bit CONFIG_GENERIC_LOCKBREAK architectures
> to kmalloc eight bytes for an indirect page table lock: the lock needs
> to fit in the space that a pointer to it would occupy, not into an int.
Ah, no. A spinlock is very much assumed to be 32bit, any spinlock that's
bigger than that is bloated.
For the page-frame case we do indeed not care about the strict 32bit but
more about not being larger than a pointer, however there are already
other users.
See for instance include/linux/lockref.h and lib/lockref.c, they very
much require the spinlock to be 32bit and the below would break that.
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: mm: ptl is not bloated if it fits in pointer
2013-12-16 9:04 ` Hugh Dickins
@ 2013-12-16 10:12 ` Peter Zijlstra
-1 siblings, 0 replies; 10+ messages in thread
From: Peter Zijlstra @ 2013-12-16 10:12 UTC (permalink / raw)
To: Hugh Dickins
Cc: Kirill A. Shutemov, Linus Torvalds, Andrew Morton, linux-kernel,
linux-mm
On Mon, Dec 16, 2013 at 01:04:13AM -0800, Hugh Dickins wrote:
> It's silly to force the 64-bit CONFIG_GENERIC_LOCKBREAK architectures
So yes that's unfortunate, but why are people using that
GENERIC_LOCKBREAK stuff to begin with? Its atrocious, a much better path
would be to remove it.
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: mm: ptl is not bloated if it fits in pointer
@ 2013-12-16 10:12 ` Peter Zijlstra
0 siblings, 0 replies; 10+ messages in thread
From: Peter Zijlstra @ 2013-12-16 10:12 UTC (permalink / raw)
To: Hugh Dickins
Cc: Kirill A. Shutemov, Linus Torvalds, Andrew Morton, linux-kernel,
linux-mm
On Mon, Dec 16, 2013 at 01:04:13AM -0800, Hugh Dickins wrote:
> It's silly to force the 64-bit CONFIG_GENERIC_LOCKBREAK architectures
So yes that's unfortunate, but why are people using that
GENERIC_LOCKBREAK stuff to begin with? Its atrocious, a much better path
would be to remove it.
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: mm: ptl is not bloated if it fits in pointer
2013-12-16 10:04 ` Peter Zijlstra
@ 2013-12-16 13:50 ` Kirill A. Shutemov
-1 siblings, 0 replies; 10+ messages in thread
From: Kirill A. Shutemov @ 2013-12-16 13:50 UTC (permalink / raw)
To: Peter Zijlstra
Cc: Hugh Dickins, Kirill A. Shutemov, Linus Torvalds, Andrew Morton,
linux-kernel, linux-mm
Peter Zijlstra wrote:
> On Mon, Dec 16, 2013 at 01:04:13AM -0800, Hugh Dickins wrote:
> > It's silly to force the 64-bit CONFIG_GENERIC_LOCKBREAK architectures
> > to kmalloc eight bytes for an indirect page table lock: the lock needs
> > to fit in the space that a pointer to it would occupy, not into an int.
>
> Ah, no. A spinlock is very much assumed to be 32bit, any spinlock that's
> bigger than that is bloated.
>
> For the page-frame case we do indeed not care about the strict 32bit but
> more about not being larger than a pointer, however there are already
> other users.
>
> See for instance include/linux/lockref.h and lib/lockref.c, they very
> much require the spinlock to be 32bit and the below would break that.
What about this instead? Smoke-tested.
>From d0243ba6bf462a7c0ae4290e1c0dbdae22eaa2a6 Mon Sep 17 00:00:00 2001
From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Date: Mon, 16 Dec 2013 15:36:31 +0200
Subject: [PATCH] mm: do not allocate page->ptl dynamically, if spinlock_t fits
to long
In struct page we have enough space to fit long-size page->ptl
there, but we use dynamically-allocated page->ptl if
size(spinlock_t) > sizeof(int). It hurts 64-bit architectures with
CONFIG_GENERIC_LOCKBREAK, where sizeof(spinlock_t) == 8, but it
easily fits into struct page.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
include/linux/lockref.h | 2 +-
include/linux/mm.h | 6 +++---
include/linux/mm_types.h | 3 ++-
kernel/bounds.c | 2 +-
mm/memory.c | 2 +-
5 files changed, 8 insertions(+), 7 deletions(-)
diff --git a/include/linux/lockref.h b/include/linux/lockref.h
index c8929c3832db..4bfde0e99ed5 100644
--- a/include/linux/lockref.h
+++ b/include/linux/lockref.h
@@ -19,7 +19,7 @@
#define USE_CMPXCHG_LOCKREF \
(IS_ENABLED(CONFIG_ARCH_USE_CMPXCHG_LOCKREF) && \
- IS_ENABLED(CONFIG_SMP) && !BLOATED_SPINLOCKS)
+ IS_ENABLED(CONFIG_SMP) && SPINLOCK_SIZE <= 4)
struct lockref {
union {
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 1cedd000cf29..35527173cf50 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1317,7 +1317,7 @@ static inline pmd_t *pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long a
#endif /* CONFIG_MMU && !__ARCH_HAS_4LEVEL_HACK */
#if USE_SPLIT_PTE_PTLOCKS
-#if BLOATED_SPINLOCKS
+#if ALLOC_SPLIT_PTLOCKS
extern bool ptlock_alloc(struct page *page);
extern void ptlock_free(struct page *page);
@@ -1325,7 +1325,7 @@ static inline spinlock_t *ptlock_ptr(struct page *page)
{
return page->ptl;
}
-#else /* BLOATED_SPINLOCKS */
+#else /* ALLOC_SPLIT_PTLOCKS */
static inline bool ptlock_alloc(struct page *page)
{
return true;
@@ -1339,7 +1339,7 @@ static inline spinlock_t *ptlock_ptr(struct page *page)
{
return &page->ptl;
}
-#endif /* BLOATED_SPINLOCKS */
+#endif /* ALLOC_SPLIT_PTLOCKS */
static inline spinlock_t *pte_lockptr(struct mm_struct *mm, pmd_t *pmd)
{
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index bd299418a934..494b328c2a61 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -26,6 +26,7 @@ struct address_space;
#define USE_SPLIT_PTE_PTLOCKS (NR_CPUS >= CONFIG_SPLIT_PTLOCK_CPUS)
#define USE_SPLIT_PMD_PTLOCKS (USE_SPLIT_PTE_PTLOCKS && \
IS_ENABLED(CONFIG_ARCH_ENABLE_SPLIT_PMD_PTLOCK))
+#define ALLOC_SPLIT_PTLOCKS (SPINLOCK_SIZE > BITS_PER_LONG/8)
/*
* Each physical page in the system has a struct page associated with
@@ -155,7 +156,7 @@ struct page {
* system if PG_buddy is set.
*/
#if USE_SPLIT_PTE_PTLOCKS
-#if BLOATED_SPINLOCKS
+#if ALLOC_SPLIT_PTLOCKS
spinlock_t *ptl;
#else
spinlock_t ptl;
diff --git a/kernel/bounds.c b/kernel/bounds.c
index 5253204afdca..9fd4246b04b8 100644
--- a/kernel/bounds.c
+++ b/kernel/bounds.c
@@ -22,6 +22,6 @@ void foo(void)
#ifdef CONFIG_SMP
DEFINE(NR_CPUS_BITS, ilog2(CONFIG_NR_CPUS));
#endif
- DEFINE(BLOATED_SPINLOCKS, sizeof(spinlock_t) > sizeof(int));
+ DEFINE(SPINLOCK_SIZE, sizeof(spinlock_t));
/* End of constants */
}
diff --git a/mm/memory.c b/mm/memory.c
index 5d9025f3b3e1..b6e211b779d0 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4271,7 +4271,7 @@ void copy_user_huge_page(struct page *dst, struct page *src,
}
#endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_HUGETLBFS */
-#if USE_SPLIT_PTE_PTLOCKS && BLOATED_SPINLOCKS
+#if ALLOC_SPLIT_PTLOCKS
bool ptlock_alloc(struct page *page)
{
spinlock_t *ptl;
--
Kirill A. Shutemov
^ permalink raw reply related [flat|nested] 10+ messages in thread
* Re: mm: ptl is not bloated if it fits in pointer
@ 2013-12-16 13:50 ` Kirill A. Shutemov
0 siblings, 0 replies; 10+ messages in thread
From: Kirill A. Shutemov @ 2013-12-16 13:50 UTC (permalink / raw)
To: Peter Zijlstra
Cc: Hugh Dickins, Kirill A. Shutemov, Linus Torvalds, Andrew Morton,
linux-kernel, linux-mm
Peter Zijlstra wrote:
> On Mon, Dec 16, 2013 at 01:04:13AM -0800, Hugh Dickins wrote:
> > It's silly to force the 64-bit CONFIG_GENERIC_LOCKBREAK architectures
> > to kmalloc eight bytes for an indirect page table lock: the lock needs
> > to fit in the space that a pointer to it would occupy, not into an int.
>
> Ah, no. A spinlock is very much assumed to be 32bit, any spinlock that's
> bigger than that is bloated.
>
> For the page-frame case we do indeed not care about the strict 32bit but
> more about not being larger than a pointer, however there are already
> other users.
>
> See for instance include/linux/lockref.h and lib/lockref.c, they very
> much require the spinlock to be 32bit and the below would break that.
What about this instead? Smoke-tested.
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: mm: ptl is not bloated if it fits in pointer
2013-12-16 13:50 ` Kirill A. Shutemov
@ 2013-12-17 0:29 ` Hugh Dickins
-1 siblings, 0 replies; 10+ messages in thread
From: Hugh Dickins @ 2013-12-17 0:29 UTC (permalink / raw)
To: Kirill A. Shutemov
Cc: Peter Zijlstra, Hugh Dickins, Linus Torvalds, Andrew Morton,
linux-kernel, linux-mm
On Mon, 16 Dec 2013, Kirill A. Shutemov wrote:
> Peter Zijlstra wrote:
> > On Mon, Dec 16, 2013 at 01:04:13AM -0800, Hugh Dickins wrote:
> > > It's silly to force the 64-bit CONFIG_GENERIC_LOCKBREAK architectures
> > > to kmalloc eight bytes for an indirect page table lock: the lock needs
> > > to fit in the space that a pointer to it would occupy, not into an int.
> >
> > Ah, no. A spinlock is very much assumed to be 32bit, any spinlock that's
> > bigger than that is bloated.
> >
> > For the page-frame case we do indeed not care about the strict 32bit but
> > more about not being larger than a pointer, however there are already
> > other users.
> >
> > See for instance include/linux/lockref.h and lib/lockref.c, they very
> > much require the spinlock to be 32bit and the below would break that.
Whoops, yes indeed, I completely missed that BLOATED_SPINLOCKS is being
used for two different purposes, which have two different constraints.
>
> What about this instead? Smoke-tested.
Excellent: I haven't tested it at all, but this patch looks to me
exactly how it should be done - thanks.
>
> From d0243ba6bf462a7c0ae4290e1c0dbdae22eaa2a6 Mon Sep 17 00:00:00 2001
> From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
> Date: Mon, 16 Dec 2013 15:36:31 +0200
> Subject: [PATCH] mm: do not allocate page->ptl dynamically, if spinlock_t fits
> to long
>
> In struct page we have enough space to fit long-size page->ptl
> there, but we use dynamically-allocated page->ptl if
> size(spinlock_t) > sizeof(int). It hurts 64-bit architectures with
> CONFIG_GENERIC_LOCKBREAK, where sizeof(spinlock_t) == 8, but it
> easily fits into struct page.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Hugh Dickins <hughd@google.com>
> ---
> include/linux/lockref.h | 2 +-
> include/linux/mm.h | 6 +++---
> include/linux/mm_types.h | 3 ++-
> kernel/bounds.c | 2 +-
> mm/memory.c | 2 +-
> 5 files changed, 8 insertions(+), 7 deletions(-)
>
> diff --git a/include/linux/lockref.h b/include/linux/lockref.h
> index c8929c3832db..4bfde0e99ed5 100644
> --- a/include/linux/lockref.h
> +++ b/include/linux/lockref.h
> @@ -19,7 +19,7 @@
>
> #define USE_CMPXCHG_LOCKREF \
> (IS_ENABLED(CONFIG_ARCH_USE_CMPXCHG_LOCKREF) && \
> - IS_ENABLED(CONFIG_SMP) && !BLOATED_SPINLOCKS)
> + IS_ENABLED(CONFIG_SMP) && SPINLOCK_SIZE <= 4)
>
> struct lockref {
> union {
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 1cedd000cf29..35527173cf50 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1317,7 +1317,7 @@ static inline pmd_t *pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long a
> #endif /* CONFIG_MMU && !__ARCH_HAS_4LEVEL_HACK */
>
> #if USE_SPLIT_PTE_PTLOCKS
> -#if BLOATED_SPINLOCKS
> +#if ALLOC_SPLIT_PTLOCKS
> extern bool ptlock_alloc(struct page *page);
> extern void ptlock_free(struct page *page);
>
> @@ -1325,7 +1325,7 @@ static inline spinlock_t *ptlock_ptr(struct page *page)
> {
> return page->ptl;
> }
> -#else /* BLOATED_SPINLOCKS */
> +#else /* ALLOC_SPLIT_PTLOCKS */
> static inline bool ptlock_alloc(struct page *page)
> {
> return true;
> @@ -1339,7 +1339,7 @@ static inline spinlock_t *ptlock_ptr(struct page *page)
> {
> return &page->ptl;
> }
> -#endif /* BLOATED_SPINLOCKS */
> +#endif /* ALLOC_SPLIT_PTLOCKS */
>
> static inline spinlock_t *pte_lockptr(struct mm_struct *mm, pmd_t *pmd)
> {
> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> index bd299418a934..494b328c2a61 100644
> --- a/include/linux/mm_types.h
> +++ b/include/linux/mm_types.h
> @@ -26,6 +26,7 @@ struct address_space;
> #define USE_SPLIT_PTE_PTLOCKS (NR_CPUS >= CONFIG_SPLIT_PTLOCK_CPUS)
> #define USE_SPLIT_PMD_PTLOCKS (USE_SPLIT_PTE_PTLOCKS && \
> IS_ENABLED(CONFIG_ARCH_ENABLE_SPLIT_PMD_PTLOCK))
> +#define ALLOC_SPLIT_PTLOCKS (SPINLOCK_SIZE > BITS_PER_LONG/8)
>
> /*
> * Each physical page in the system has a struct page associated with
> @@ -155,7 +156,7 @@ struct page {
> * system if PG_buddy is set.
> */
> #if USE_SPLIT_PTE_PTLOCKS
> -#if BLOATED_SPINLOCKS
> +#if ALLOC_SPLIT_PTLOCKS
> spinlock_t *ptl;
> #else
> spinlock_t ptl;
> diff --git a/kernel/bounds.c b/kernel/bounds.c
> index 5253204afdca..9fd4246b04b8 100644
> --- a/kernel/bounds.c
> +++ b/kernel/bounds.c
> @@ -22,6 +22,6 @@ void foo(void)
> #ifdef CONFIG_SMP
> DEFINE(NR_CPUS_BITS, ilog2(CONFIG_NR_CPUS));
> #endif
> - DEFINE(BLOATED_SPINLOCKS, sizeof(spinlock_t) > sizeof(int));
> + DEFINE(SPINLOCK_SIZE, sizeof(spinlock_t));
> /* End of constants */
> }
> diff --git a/mm/memory.c b/mm/memory.c
> index 5d9025f3b3e1..b6e211b779d0 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -4271,7 +4271,7 @@ void copy_user_huge_page(struct page *dst, struct page *src,
> }
> #endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_HUGETLBFS */
>
> -#if USE_SPLIT_PTE_PTLOCKS && BLOATED_SPINLOCKS
> +#if ALLOC_SPLIT_PTLOCKS
> bool ptlock_alloc(struct page *page)
> {
> spinlock_t *ptl;
> --
> Kirill A. Shutemov
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: mm: ptl is not bloated if it fits in pointer
@ 2013-12-17 0:29 ` Hugh Dickins
0 siblings, 0 replies; 10+ messages in thread
From: Hugh Dickins @ 2013-12-17 0:29 UTC (permalink / raw)
To: Kirill A. Shutemov
Cc: Peter Zijlstra, Hugh Dickins, Linus Torvalds, Andrew Morton,
linux-kernel, linux-mm
On Mon, 16 Dec 2013, Kirill A. Shutemov wrote:
> Peter Zijlstra wrote:
> > On Mon, Dec 16, 2013 at 01:04:13AM -0800, Hugh Dickins wrote:
> > > It's silly to force the 64-bit CONFIG_GENERIC_LOCKBREAK architectures
> > > to kmalloc eight bytes for an indirect page table lock: the lock needs
> > > to fit in the space that a pointer to it would occupy, not into an int.
> >
> > Ah, no. A spinlock is very much assumed to be 32bit, any spinlock that's
> > bigger than that is bloated.
> >
> > For the page-frame case we do indeed not care about the strict 32bit but
> > more about not being larger than a pointer, however there are already
> > other users.
> >
> > See for instance include/linux/lockref.h and lib/lockref.c, they very
> > much require the spinlock to be 32bit and the below would break that.
Whoops, yes indeed, I completely missed that BLOATED_SPINLOCKS is being
used for two different purposes, which have two different constraints.
>
> What about this instead? Smoke-tested.
Excellent: I haven't tested it at all, but this patch looks to me
exactly how it should be done - thanks.
>
> From d0243ba6bf462a7c0ae4290e1c0dbdae22eaa2a6 Mon Sep 17 00:00:00 2001
> From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
> Date: Mon, 16 Dec 2013 15:36:31 +0200
> Subject: [PATCH] mm: do not allocate page->ptl dynamically, if spinlock_t fits
> to long
>
> In struct page we have enough space to fit long-size page->ptl
> there, but we use dynamically-allocated page->ptl if
> size(spinlock_t) > sizeof(int). It hurts 64-bit architectures with
> CONFIG_GENERIC_LOCKBREAK, where sizeof(spinlock_t) == 8, but it
> easily fits into struct page.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Hugh Dickins <hughd@google.com>
> ---
> include/linux/lockref.h | 2 +-
> include/linux/mm.h | 6 +++---
> include/linux/mm_types.h | 3 ++-
> kernel/bounds.c | 2 +-
> mm/memory.c | 2 +-
> 5 files changed, 8 insertions(+), 7 deletions(-)
>
> diff --git a/include/linux/lockref.h b/include/linux/lockref.h
> index c8929c3832db..4bfde0e99ed5 100644
> --- a/include/linux/lockref.h
> +++ b/include/linux/lockref.h
> @@ -19,7 +19,7 @@
>
> #define USE_CMPXCHG_LOCKREF \
> (IS_ENABLED(CONFIG_ARCH_USE_CMPXCHG_LOCKREF) && \
> - IS_ENABLED(CONFIG_SMP) && !BLOATED_SPINLOCKS)
> + IS_ENABLED(CONFIG_SMP) && SPINLOCK_SIZE <= 4)
>
> struct lockref {
> union {
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 1cedd000cf29..35527173cf50 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1317,7 +1317,7 @@ static inline pmd_t *pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long a
> #endif /* CONFIG_MMU && !__ARCH_HAS_4LEVEL_HACK */
>
> #if USE_SPLIT_PTE_PTLOCKS
> -#if BLOATED_SPINLOCKS
> +#if ALLOC_SPLIT_PTLOCKS
> extern bool ptlock_alloc(struct page *page);
> extern void ptlock_free(struct page *page);
>
> @@ -1325,7 +1325,7 @@ static inline spinlock_t *ptlock_ptr(struct page *page)
> {
> return page->ptl;
> }
> -#else /* BLOATED_SPINLOCKS */
> +#else /* ALLOC_SPLIT_PTLOCKS */
> static inline bool ptlock_alloc(struct page *page)
> {
> return true;
> @@ -1339,7 +1339,7 @@ static inline spinlock_t *ptlock_ptr(struct page *page)
> {
> return &page->ptl;
> }
> -#endif /* BLOATED_SPINLOCKS */
> +#endif /* ALLOC_SPLIT_PTLOCKS */
>
> static inline spinlock_t *pte_lockptr(struct mm_struct *mm, pmd_t *pmd)
> {
> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> index bd299418a934..494b328c2a61 100644
> --- a/include/linux/mm_types.h
> +++ b/include/linux/mm_types.h
> @@ -26,6 +26,7 @@ struct address_space;
> #define USE_SPLIT_PTE_PTLOCKS (NR_CPUS >= CONFIG_SPLIT_PTLOCK_CPUS)
> #define USE_SPLIT_PMD_PTLOCKS (USE_SPLIT_PTE_PTLOCKS && \
> IS_ENABLED(CONFIG_ARCH_ENABLE_SPLIT_PMD_PTLOCK))
> +#define ALLOC_SPLIT_PTLOCKS (SPINLOCK_SIZE > BITS_PER_LONG/8)
>
> /*
> * Each physical page in the system has a struct page associated with
> @@ -155,7 +156,7 @@ struct page {
> * system if PG_buddy is set.
> */
> #if USE_SPLIT_PTE_PTLOCKS
> -#if BLOATED_SPINLOCKS
> +#if ALLOC_SPLIT_PTLOCKS
> spinlock_t *ptl;
> #else
> spinlock_t ptl;
> diff --git a/kernel/bounds.c b/kernel/bounds.c
> index 5253204afdca..9fd4246b04b8 100644
> --- a/kernel/bounds.c
> +++ b/kernel/bounds.c
> @@ -22,6 +22,6 @@ void foo(void)
> #ifdef CONFIG_SMP
> DEFINE(NR_CPUS_BITS, ilog2(CONFIG_NR_CPUS));
> #endif
> - DEFINE(BLOATED_SPINLOCKS, sizeof(spinlock_t) > sizeof(int));
> + DEFINE(SPINLOCK_SIZE, sizeof(spinlock_t));
> /* End of constants */
> }
> diff --git a/mm/memory.c b/mm/memory.c
> index 5d9025f3b3e1..b6e211b779d0 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -4271,7 +4271,7 @@ void copy_user_huge_page(struct page *dst, struct page *src,
> }
> #endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_HUGETLBFS */
>
> -#if USE_SPLIT_PTE_PTLOCKS && BLOATED_SPINLOCKS
> +#if ALLOC_SPLIT_PTLOCKS
> bool ptlock_alloc(struct page *page)
> {
> spinlock_t *ptl;
> --
> Kirill A. Shutemov
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^ permalink raw reply [flat|nested] 10+ messages in thread
end of thread, other threads:[~2013-12-17 0:30 UTC | newest]
Thread overview: 10+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2013-12-16 9:04 mm: ptl is not bloated if it fits in pointer Hugh Dickins
2013-12-16 9:04 ` Hugh Dickins
2013-12-16 10:04 ` Peter Zijlstra
2013-12-16 10:04 ` Peter Zijlstra
2013-12-16 13:50 ` Kirill A. Shutemov
2013-12-16 13:50 ` Kirill A. Shutemov
2013-12-17 0:29 ` Hugh Dickins
2013-12-17 0:29 ` Hugh Dickins
2013-12-16 10:12 ` Peter Zijlstra
2013-12-16 10:12 ` Peter Zijlstra
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