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From 40e5fe48b1d42c22b670f707a43646251e505b4f Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@infradead.org>
Date: Fri, 3 Jul 2009 08:44:54 -0500
Subject: [PATCH 098/271] mm: shrink the page frame to !-rt size
He below is a boot-tested hack to shrink the page frame size back to
normal.
Should be a net win since there should be many less PTE-pages than
page-frames.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
include/linux/mm.h | 46 +++++++++++++++++++++++++++++++++++++++-------
include/linux/mm_types.h | 6 +++++-
mm/memory.c | 32 ++++++++++++++++++++++++++++++++
3 files changed, 76 insertions(+), 8 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 441a564..abc98ef 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1200,27 +1200,59 @@ static inline pmd_t *pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long a
* overflow into the next struct page (as it might with DEBUG_SPINLOCK).
* When freeing, reset page->mapping so free_pages_check won't complain.
*/
+#ifndef CONFIG_PREEMPT_RT_FULL
+
#define __pte_lockptr(page) &((page)->ptl)
-#define pte_lock_init(_page) do { \
- spin_lock_init(__pte_lockptr(_page)); \
-} while (0)
+
+static inline struct page *pte_lock_init(struct page *page)
+{
+ spin_lock_init(__pte_lockptr(page));
+ return page;
+}
+
#define pte_lock_deinit(page) ((page)->mapping = NULL)
+
+#else /* !PREEMPT_RT_FULL */
+
+/*
+ * On PREEMPT_RT_FULL the spinlock_t's are too large to embed in the
+ * page frame, hence it only has a pointer and we need to dynamically
+ * allocate the lock when we allocate PTE-pages.
+ *
+ * This is an overall win, since only a small fraction of the pages
+ * will be PTE pages under normal circumstances.
+ */
+
+#define __pte_lockptr(page) ((page)->ptl)
+
+extern struct page *pte_lock_init(struct page *page);
+extern void pte_lock_deinit(struct page *page);
+
+#endif /* PREEMPT_RT_FULL */
+
#define pte_lockptr(mm, pmd) ({(void)(mm); __pte_lockptr(pmd_page(*(pmd)));})
#else /* !USE_SPLIT_PTLOCKS */
/*
* We use mm->page_table_lock to guard all pagetable pages of the mm.
*/
-#define pte_lock_init(page) do {} while (0)
+static inline struct page *pte_lock_init(struct page *page) { return page; }
#define pte_lock_deinit(page) do {} while (0)
#define pte_lockptr(mm, pmd) ({(void)(pmd); &(mm)->page_table_lock;})
#endif /* USE_SPLIT_PTLOCKS */
-static inline void pgtable_page_ctor(struct page *page)
+static inline struct page *__pgtable_page_ctor(struct page *page)
{
- pte_lock_init(page);
- inc_zone_page_state(page, NR_PAGETABLE);
+ page = pte_lock_init(page);
+ if (page)
+ inc_zone_page_state(page, NR_PAGETABLE);
+ return page;
}
+#define pgtable_page_ctor(page) \
+do { \
+ page = __pgtable_page_ctor(page); \
+} while (0)
+
static inline void pgtable_page_dtor(struct page *page)
{
pte_lock_deinit(page);
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index b35752f..b01cd4b 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -128,7 +128,11 @@ struct page {
* system if PG_buddy is set.
*/
#if USE_SPLIT_PTLOCKS
- spinlock_t ptl;
+# ifndef CONFIG_PREEMPT_RT_FULL
+ spinlock_t ptl;
+# else
+ spinlock_t *ptl;
+# endif
#endif
struct kmem_cache *slab; /* SLUB: Pointer to slab */
struct page *first_page; /* Compound tail pages */
diff --git a/mm/memory.c b/mm/memory.c
index 346246c..68676fd 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4033,3 +4033,35 @@ void copy_user_huge_page(struct page *dst, struct page *src,
}
}
#endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_HUGETLBFS */
+
+#if defined(CONFIG_PREEMPT_RT_FULL) && (USE_SPLIT_PTLOCKS > 0)
+/*
+ * Heinous hack, relies on the caller doing something like:
+ *
+ * pte = alloc_pages(PGALLOC_GFP, 0);
+ * if (pte)
+ * pgtable_page_ctor(pte);
+ * return pte;
+ *
+ * This ensures we release the page and return NULL when the
+ * lock allocation fails.
+ */
+struct page *pte_lock_init(struct page *page)
+{
+ page->ptl = kmalloc(sizeof(spinlock_t), GFP_KERNEL);
+ if (page->ptl) {
+ spin_lock_init(__pte_lockptr(page));
+ } else {
+ __free_page(page);
+ page = NULL;
+ }
+ return page;
+}
+
+void pte_lock_deinit(struct page *page)
+{
+ kfree(page->ptl);
+ page->mapping = NULL;
+}
+
+#endif
--
1.7.10.4
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