mm: implement split page table lock for PMD level

The basic idea is the same as with PTE level: the lock is embedded into struct page of table's page. We can't use mm->pmd_huge_pte to store pgtables for THP, since we don't take mm->page_table_lock anymore. Let's reuse page->lru of table's page for that. pgtable_pmd_page_ctor() returns true, if initialization is successful and false otherwise. Current implementation never fails, but assumption that constructor can fail will help to port it to -rt where spinlock_t is rather huge and cannot be embedded into struct page -- dynamic allocation is required.

Kirill A. Shutemov committed 13 years ago

Commit e009bb31 parent c4088eb4 files · +43 −3Browse files

Showing the changes to kernel (1 of 4 files). Show all

Unified · Split

kernel/fork.c+2−2

@@ -560,7 +560,7 @@ static void check_mm(struct mm_struct *mm) · 559 unmodified lines
560	560	"mm:%p idx:%d val:%ld\n", mm, i, x);
561	561	}
562	562
563		−#ifdef CONFIG_TRANSPARENT_HUGEPAGE
	563	+#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
564	564	VM_BUG_ON(mm->pmd_huge_pte);
565	565	#endif
566	566	}
@@ -814,7 +814,7 @@ struct mm_struct dup_mm(struct task_struct tsk) · 247 unmodified lines
814	814	memcpy(mm, oldmm, sizeof(*mm));
815	815	mm_init_cpumask(mm);
816	816
817		−#ifdef CONFIG_TRANSPARENT_HUGEPAGE
	817	+#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
818	818	mm->pmd_huge_pte = NULL;
819	819	#endif
820	820	if (!mm_init(mm, tsk))