Messages in this thread Patch in this message | | | Date | Fri, 29 Apr 2005 12:59:17 -0700 (PDT) | From | Christoph Lameter <> | Subject | [PATCH 3/3] Page Fault Scalability V20: Avoid lock for anonymous write fault |
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Do not use the page_table_lock in do_anonymous_page. This will significantly increase the parallelism in the page fault handler for SMP systems. The patch also modifies the definitions of _mm_counter functions so that rss and anon_rss become atomic (and will use atomic64_t if available).
For the benefit of these performance enhancements see the charts at http://oss.sgi.com/projects/page_fault_performance/atomic-ptes.pdf
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Index: linux-2.6.11/mm/memory.c =================================================================== --- linux-2.6.11.orig/mm/memory.c 2005-04-29 10:31:50.000000000 -0700 +++ linux-2.6.11/mm/memory.c 2005-04-29 10:33:06.000000000 -0700 @@ -1790,12 +1790,12 @@ do_anonymous_page(struct mm_struct *mm, entry = maybe_mkwrite(pte_mkdirty(mk_pte(page, vma->vm_page_prot)), vma); - spin_lock(&mm->page_table_lock); + page_table_atomic_start(mm); if (!ptep_cmpxchg(mm, addr, page_table, orig_entry, entry)) { pte_unmap(page_table); page_cache_release(page); - spin_unlock(&mm->page_table_lock); + page_table_atomic_stop(mm); inc_page_state(cmpxchg_fail_anon_write); return VM_FAULT_MINOR; } @@ -1811,7 +1811,7 @@ do_anonymous_page(struct mm_struct *mm, pte_unmap(page_table); update_mmu_cache(vma, addr, entry); lazy_mmu_prot_update(entry); - spin_unlock(&mm->page_table_lock); + page_table_atomic_stop(mm); return VM_FAULT_MINOR; } Index: linux-2.6.11/include/linux/sched.h =================================================================== --- linux-2.6.11.orig/include/linux/sched.h 2005-04-29 08:25:55.000000000 -0700 +++ linux-2.6.11/include/linux/sched.h 2005-04-29 10:33:06.000000000 -0700 @@ -204,12 +204,43 @@ arch_get_unmapped_area_topdown(struct fi extern void arch_unmap_area(struct vm_area_struct *area); extern void arch_unmap_area_topdown(struct vm_area_struct *area); +#ifdef CONFIG_ATOMIC_TABLE_OPS +/* + * No spinlock is held during atomic page table operations. The + * counters are not protected anymore and must also be + * incremented atomically. +*/ +#ifdef ATOMIC64_INIT +#define set_mm_counter(mm, member, value) atomic64_set(&(mm)->_##member, value) +#define get_mm_counter(mm, member) ((unsigned long)atomic64_read(&(mm)->_##member)) +#define add_mm_counter(mm, member, value) atomic64_add(value, &(mm)->_##member) +#define inc_mm_counter(mm, member) atomic64_dec(&(mm)->_##member) +#define dec_mm_counter(mm, member) atomic64_dec(&(mm)->_##member) +typedef atomic64_t mm_counter_t; +#else +/* + * This may limit process memory to 2^31 * PAGE_SIZE which may be around 8TB + * if using 4KB page size + */ +#define set_mm_counter(mm, member, value) atomic_set(&(mm)->_##member, value) +#define get_mm_counter(mm, member) ((unsigned long)atomic_read(&(mm)->_##member)) +#define add_mm_counter(mm, member, value) atomic_add(value, &(mm)->_##member) +#define inc_mm_counter(mm, member) atomic_inc(&(mm)->_##member) +#define dec_mm_counter(mm, member) atomic_dec(&(mm)->_##member) +typedef atomic_t mm_counter_t; +#endif +#else +/* + * No atomic page table operations. Counters are protected by + * the page table lock + */ #define set_mm_counter(mm, member, value) (mm)->_##member = (value) #define get_mm_counter(mm, member) ((mm)->_##member) #define add_mm_counter(mm, member, value) (mm)->_##member += (value) #define inc_mm_counter(mm, member) (mm)->_##member++ #define dec_mm_counter(mm, member) (mm)->_##member-- typedef unsigned long mm_counter_t; +#endif struct mm_struct { struct vm_area_struct * mmap; /* list of VMAs */ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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