@@ -111,7 +111,16 @@ static inline pud_t *pud_alloc_one(struct mm_struct *mm, unsigned long addr)
static inline void pud_free(struct mm_struct *mm, pud_t *pud)
{
- kmem_cache_free(PGT_CACHE(PUD_CACHE_INDEX), pud);
+ struct page *page = virt_to_page(pud);
+
+ /*
+ * Early pud pages allocated via memblock allocator
+ * can't be directly freed to slab
+ */
+ if (PageReserved(page))
+ free_reserved_page(page);
+ else
+ kmem_cache_free(PGT_CACHE(PUD_CACHE_INDEX), pud);
}
static inline void pud_populate(struct mm_struct *mm, pud_t *pud, pmd_t *pmd)
@@ -288,6 +288,7 @@ static inline unsigned long radix__get_tree_size(void)
#ifdef CONFIG_MEMORY_HOTPLUG
int radix__create_section_mapping(unsigned long start, unsigned long end, int nid);
int radix__remove_section_mapping(unsigned long start, unsigned long end);
+void radix__fixup_pgtable_fragments(void);
#endif /* CONFIG_MEMORY_HOTPLUG */
#endif /* __ASSEMBLY__ */
#endif
@@ -15,6 +15,7 @@
#ifdef CONFIG_MEMORY_HOTPLUG
extern int create_section_mapping(unsigned long start, unsigned long end, int nid);
extern int remove_section_mapping(unsigned long start, unsigned long end);
+void fixup_pgtable_fragments(void);
#ifdef CONFIG_PPC_BOOK3S_64
extern int resize_hpt_for_hotplug(unsigned long new_mem_size);
@@ -186,6 +186,13 @@ int __meminit remove_section_mapping(unsigned long start, unsigned long end)
return hash__remove_section_mapping(start, end);
}
+
+void fixup_pgtable_fragments(void)
+{
+ if (radix_enabled())
+ radix__fixup_pgtable_fragments();
+}
+
#endif /* CONFIG_MEMORY_HOTPLUG */
void __init mmu_partition_table_init(void)
@@ -319,13 +326,23 @@ void pmd_fragment_free(unsigned long *pmd)
BUG_ON(atomic_read(&page->pt_frag_refcount) <= 0);
if (atomic_dec_and_test(&page->pt_frag_refcount)) {
- pgtable_pmd_page_dtor(page);
- __free_page(page);
+ /*
+ * Early pmd pages allocated via memblock
+ * allocator wouldn't have called _ctor
+ */
+ if (PageReserved(page))
+ free_reserved_page(page);
+ else {
+ pgtable_pmd_page_dtor(page);
+ __free_page(page);
+ }
}
}
static inline void pgtable_free(void *table, int index)
{
+ struct page *page;
+
switch (index) {
case PTE_INDEX:
pte_fragment_free(table, 0);
@@ -334,7 +351,15 @@ static inline void pgtable_free(void *table, int index)
pmd_fragment_free(table);
break;
case PUD_INDEX:
- kmem_cache_free(PGT_CACHE(PUD_CACHE_INDEX), table);
+ page = virt_to_page(table);
+ /*
+ * Early pud pages allocated via memblock
+ * allocator need to be freed differently
+ */
+ if (PageReserved(page))
+ free_reserved_page(page);
+ else
+ kmem_cache_free(PGT_CACHE(PUD_CACHE_INDEX), table);
break;
#if defined(CONFIG_PPC_4K_PAGES) && defined(CONFIG_HUGETLB_PAGE)
/* 16M hugepd directory at pud level */
@@ -33,6 +33,70 @@
unsigned int mmu_pid_bits;
unsigned int mmu_base_pid;
+static void fixup_pte_fragments(pmd_t *pmd)
+{
+ int i;
+
+ for (i = 0; i < PTRS_PER_PMD; i++, pmd++) {
+ pte_t *pte;
+ struct page *page;
+
+ if (pmd_none(*pmd))
+ continue;
+ if (pmd_is_leaf(*pmd))
+ continue;
+
+ pte = pte_offset_kernel(pmd, 0);
+ page = virt_to_page(pte);
+ atomic_inc(&page->pt_frag_refcount);
+ }
+}
+
+static void fixup_pmd_fragments(pud_t *pud)
+{
+ int i;
+
+ for (i = 0; i < PTRS_PER_PUD; i++, pud++) {
+ pmd_t *pmd;
+ struct page *page;
+
+ if (pud_none(*pud))
+ continue;
+ if (pud_is_leaf(*pud))
+ continue;
+
+ pmd = pmd_offset(pud, 0);
+ page = virt_to_page(pmd);
+ atomic_inc(&page->pt_frag_refcount);
+ fixup_pte_fragments(pmd);
+ }
+}
+
+/*
+ * Walk the init_mm page tables and fixup the PMD and PTE fragment
+ * counts. This allows the PUD, PMD and PTE pages to be freed
+ * back to buddy allocator properly during memory unplug.
+ */
+void radix__fixup_pgtable_fragments(void)
+{
+ int i;
+ pgd_t *pgd = pgd_offset_k(0UL);
+
+ spin_lock(&init_mm.page_table_lock);
+ for (i = 0; i < PTRS_PER_PGD; i++, pgd++) {
+ pud_t *pud;
+
+ if (pgd_none(*pgd))
+ continue;
+ if (pgd_is_leaf(*pgd))
+ continue;
+
+ pud = pud_offset(pgd, 0);
+ fixup_pmd_fragments(pud);
+ }
+ spin_unlock(&init_mm.page_table_lock);
+}
+
static int native_register_process_table(unsigned long base, unsigned long pg_sz,
unsigned long table_size)
{
@@ -81,7 +145,7 @@ static int early_map_kernel_page(unsigned long ea, unsigned long pa,
pgdp = pgd_offset_k(ea);
if (pgd_none(*pgdp)) {
- pudp = early_alloc_pgtable(PUD_TABLE_SIZE, nid,
+ pudp = early_alloc_pgtable(PAGE_SIZE, nid,
region_start, region_end);
pgd_populate(&init_mm, pgdp, pudp);
}
@@ -91,7 +155,7 @@ static int early_map_kernel_page(unsigned long ea, unsigned long pa,
goto set_the_pte;
}
if (pud_none(*pudp)) {
- pmdp = early_alloc_pgtable(PMD_TABLE_SIZE, nid,
+ pmdp = early_alloc_pgtable(PAGE_SIZE, nid,
region_start, region_end);
pud_populate(&init_mm, pudp, pmdp);
}
@@ -51,6 +51,10 @@
#include <mm/mmu_decl.h>
+void __weak fixup_pgtable_fragments(void)
+{
+}
+
#ifndef CPU_FTR_COHERENT_ICACHE
#define CPU_FTR_COHERENT_ICACHE 0 /* XXX for now */
#define CPU_FTR_NOEXECUTE 0
@@ -267,6 +271,7 @@ void __init mem_init(void)
set_max_mapnr(max_pfn);
memblock_free_all();
+ fixup_pgtable_fragments();
#ifdef CONFIG_HIGHMEM
{
unsigned long pfn, highmem_mapnr;
@@ -114,6 +114,13 @@ void pte_fragment_free(unsigned long *table, int kernel)
if (atomic_dec_and_test(&page->pt_frag_refcount)) {
if (!kernel)
pgtable_page_dtor(page);
- __free_page(page);
+ /*
+ * Early pte pages allocated via memblock
+ * allocator need to be freed differently
+ */
+ if (PageReserved(page))
+ free_reserved_page(page);
+ else
+ __free_page(page);
}
}
We can hit the following BUG_ONs during memory unplug kernel BUG at arch/powerpc/mm/pgtable-frag.c:113! remove_pagetable+0x594/0x6a0 (unreliable) remove_pagetable+0x94/0x6a0 vmemmap_free+0x394/0x410 sparse_remove_one_section+0x26c/0x2e8 __remove_pages+0x428/0x540 arch_remove_memory+0xd0/0x170 __remove_memory+0xd4/0x1a0 dlpar_remove_lmb+0xbc/0x110 dlpar_memory+0xa80/0xd20 handle_dlpar_errorlog+0xa8/0x160 pseries_hp_work_fn+0x2c/0x60 process_one_work+0x46c/0x860 worker_thread+0x364/0x5e0 kthread+0x1b0/0x1c0 ret_from_kernel_thread+0x5c/0x68 kernel BUG at arch/powerpc/mm/book3s64/pgtable.c:331! remove_pagetable+0x604/0x6a0 (unreliable) remove_pagetable+0x2cc/0x6a0 radix__remove_section_mapping+0x18/0x2c remove_section_mapping+0x8c/0xb0 arch_remove_memory+0xf8/0x160 __remove_memory+0xd4/0x190 dlpar_remove_lmb+0xbc/0x110 dlpar_memory+0xa90/0xd30 handle_dlpar_errorlog+0xa8/0x160 pseries_hp_work_fn+0x2c/0x60 process_one_work+0x46c/0x860 worker_thread+0x364/0x5e0 kthread+0x1b0/0x1c0 ret_from_kernel_thread+0x5c/0x68 These occur when unplug is attempted for such memory which has been mapped using memblock pages as part of early kernel page table setup. We wouldn't have initialized the PMD or PTE fragment count for those PMD or PTE pages. Fixing this includes 3 parts: - Re-walk the init_mm page tables from mem_init() and initialize the PMD and PTE fragment count to 1. - When freeing PUD, PMD and PTE page table pages, check explicitly if they come from memblock and if so free then appropriately. - When we do early memblock based allocation of PMD and PUD pages, allocate in PAGE_SIZE granularity so that we are sure the complete page is used as pagetable page. Since we now do PAGE_SIZE allocations for both PUD table and PMD table (Note that PTE table allocation is already of PAGE_SIZE), we end up allocating more memory for the same amount of system RAM. Here is a comparision of how much more we need for a 64T and 2G system after this patch: 1. 64T system ------------- 64T RAM would need 64G for vmemmap with struct page size being 64B. 128 PUD tables for 64T memory (1G mappings) 1 PUD table and 64 PMD tables for 64G vmemmap (2M mappings) With default PUD[PMD]_TABLE_SIZE(4K), (128+1+64)*4K=772K With PAGE_SIZE(64K) table allocations, (128+1+64)*64K=12352K 2. 2G system ------------ 2G RAM would need 2M for vmemmap with struct page size being 64B. 1 PUD table for 2G memory (1G mapping) 1 PUD table and 1 PMD table for 2M vmemmap (2M mappings) With default PUD[PMD]_TABLE_SIZE(4K), (1+1+1)*4K=12K With new PAGE_SIZE(64K) table allocations, (1+1+1)*64K=192K Reported-by: Srikanth Aithal <sraithal@linux.vnet.ibm.com> Signed-off-by: Bharata B Rao <bharata@linux.ibm.com> --- Changes in v3: - Commit message corrections and added example to show the extra memory usage for a small(2G) system in addition to 64T system. - Handle freeing of memblock allocated page table pages separately for PUD, PMD and PTE pages. I had earlier converted the PMD and PTE from reserved to normal pages during fragments fixup so that they can be freed w/o special casing them. However that won't work because there are slight differences b/n these three types of pages: - Kernel PTE pages don't need _dtor routines to be run - PMD pages need _dtor routines to be run for all pages (Removing _ctor setup and ptlock init for kernel PMD pages is an optimization that can be done separately) - PUD pages go to kmem_cache during free So in anycase these 3 types need to be handled differently. arch/powerpc/include/asm/book3s/64/pgalloc.h | 11 +++- arch/powerpc/include/asm/book3s/64/radix.h | 1 + arch/powerpc/include/asm/sparsemem.h | 1 + arch/powerpc/mm/book3s64/pgtable.c | 31 ++++++++- arch/powerpc/mm/book3s64/radix_pgtable.c | 68 +++++++++++++++++++- arch/powerpc/mm/mem.c | 5 ++ arch/powerpc/mm/pgtable-frag.c | 9 ++- 7 files changed, 119 insertions(+), 7 deletions(-)