page fault scalability patch V11 [1/7]: sloppy rss

Christoph Lameter
2004-11-19T19:43:30Z

Changelog
* Enable the sloppy use of mm->rss and mm->anon_rss atomic without locking
* Insure that negative rss values are not given out by the /proc filesystem
* remove 3 checks of rss in mm/rmap.c
* Prerequisite for page table scalability patch

Signed-off-by: Christoph Lameter <clameter@sgi.com>

Index: linux-2.6.9/include/linux/sched.h
=================================--- linux-2.6.9.orig/include/linux/sched.h 2004-11-15 11:13:39.000000000 -0800
+++ linux-2.6.9/include/linux/sched.h 2004-11-18 13:04:30.000000000 -0800
@@ -216,7 +216,7 @@
atomic_t mm_count; /* How many references to "struct mm_struct" (users count as 1) */
int map_count; /* number of VMAs */
struct rw_semaphore mmap_sem;
- spinlock_t page_table_lock; /* Protects page tables, mm->rss, mm->anon_rss */
+ spinlock_t page_table_lock; /* Protects page tables */

struct list_head mmlist; /* List of maybe swapped mm's. These are globally strung
* together off init_mm.mmlist, and are protected
@@ -252,6 +252,21 @@
struct kioctx default_kioctx;
};

+/*
+ * rss and anon_rss are incremented and decremented in some locations without
+ * proper locking. This function insures that these values do not become negative.
+ */
+static long inline get_rss(struct mm_struct *mm)
+{
+ long rss = mm->rss;
+
+ if (rss < 0)
+ mm->rss = rss = 0;
+ if ((long)mm->anon_rss < 0)
+ mm->anon_rss = 0;
+ return rss;
+}
+
struct sighand_struct {
atomic_t count;
struct k_sigaction action[_NSIG];
Index: linux-2.6.9/fs/proc/task_mmu.c
=================================--- linux-2.6.9.orig/fs/proc/task_mmu.c 2004-11-15 11:13:38.000000000 -0800
+++ linux-2.6.9/fs/proc/task_mmu.c 2004-11-18 12:56:26.000000000 -0800
@@ -22,7 +22,7 @@
"VmPTE:\t%8lu kB\n",
(mm->total_vm - mm->reserved_vm) << (PAGE_SHIFT-10),
mm->locked_vm << (PAGE_SHIFT-10),
- mm->rss << (PAGE_SHIFT-10),
+ get_rss(mm) << (PAGE_SHIFT-10),
data << (PAGE_SHIFT-10),
mm->stack_vm << (PAGE_SHIFT-10), text, lib,
(PTRS_PER_PTE*sizeof(pte_t)*mm->nr_ptes) >> 10);
@@ -37,7 +37,9 @@
int task_statm(struct mm_struct *mm, int *shared, int *text,
int *data, int *resident)
{
- *shared = mm->rss - mm->anon_rss;
+ *shared = get_rss(mm) - mm->anon_rss;
+ if (*shared <0)
+ *shared = 0;
*text = (PAGE_ALIGN(mm->end_code) - (mm->start_code & PAGE_MASK))
>> PAGE_SHIFT;
*data = mm->total_vm - mm->shared_vm;
Index: linux-2.6.9/fs/proc/array.c
=================================--- linux-2.6.9.orig/fs/proc/array.c 2004-11-15 11:13:38.000000000 -0800
+++ linux-2.6.9/fs/proc/array.c 2004-11-18 12:53:16.000000000 -0800
@@ -420,7 +420,7 @@
jiffies_to_clock_t(task->it_real_value),
start_time,
vsize,
- mm ? mm->rss : 0, /* you might want to shift this left 3 */
+ mm ? get_rss(mm) : 0, /* you might want to shift this left 3 */
rsslim,
mm ? mm->start_code : 0,
mm ? mm->end_code : 0,
Index: linux-2.6.9/mm/rmap.c
=================================--- linux-2.6.9.orig/mm/rmap.c 2004-11-15 11:13:40.000000000 -0800
+++ linux-2.6.9/mm/rmap.c 2004-11-18 12:26:45.000000000 -0800
@@ -263,8 +263,6 @@
pte_t *pte;
int referenced = 0;

- if (!mm->rss)
- goto out;
address = vma_address(page, vma);
if (address = -EFAULT)
goto out;
@@ -504,8 +502,6 @@
pte_t pteval;
int ret = SWAP_AGAIN;

- if (!mm->rss)
- goto out;
address = vma_address(page, vma);
if (address = -EFAULT)
goto out;
@@ -788,8 +784,7 @@
if (vma->vm_flags & (VM_LOCKED|VM_RESERVED))
continue;
cursor = (unsigned long) vma->vm_private_data;
- while (vma->vm_mm->rss &&
- cursor < max_nl_cursor &&
+ while (cursor < max_nl_cursor &&
cursor < vma->vm_end - vma->vm_start) {
try_to_unmap_cluster(cursor, &mapcount, vma);
cursor += CLUSTER_SIZE;