O(1) proc_pid_statm()

From: William Lee Irwin III
Date: Tue Aug 24 2004 - 02:57:50 EST

On Mon, Aug 23, 2004 at 11:14:54PM -0700, Andrew Morton wrote:
> I'd prefer it if you (and everyone else) could give a meaningful
> English-language Subject: to patches, please.
> A well-chosen patch Subject: becomes a sort of globally-unique key by which
> the patch is tracked - I munge it into a patch filename and it propagates
> all the way into bitkeeper. It can be used for searching email folders,
> googling, inter-developer discussion, etc, etc.

Is this better?

Merely removing down_read(&mm->mmap_sem) from task_vsize() is too
half-assed to let stand. The following patch removes the vma iteration
as well as the down_read(&mm->mmap_sem) from both task_mem() and
task_statm() and callers for the CONFIG_MMU=y case in favor of
accounting the various stats reported at the times of vma creation,
destruction, and modification. Unlike the 2.4.x patches of the same
name, this has no per-pte-modification overhead whatsoever.

This patch quashes end user complaints of top(1) being slow as well as
kernel hacker complaints of per-pte accounting overhead simultaneously.

Incremental atop the task_vsize() de-mmap_sem-ification of 2.6.8.1-mm4:


Index: mm4-2.6.8.1/arch/ia64/ia32/binfmt_elf32.c
===================================================================
--- mm4-2.6.8.1.orig/arch/ia64/ia32/binfmt_elf32.c 2004-08-14 03:56:22.000000000 -0700
+++ mm4-2.6.8.1/arch/ia64/ia32/binfmt_elf32.c 2004-08-23 23:29:21.860506592 -0700
@@ -187,7 +187,7 @@
mpnt->vm_page_prot = (mpnt->vm_flags & VM_EXEC)?
PAGE_COPY_EXEC: PAGE_COPY;
insert_vm_struct(current->mm, mpnt);
- current->mm->total_vm = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
+ current->mm->stack_vm = current->mm->total_vm = vma_pages(mpnt);
}

for (i = 0 ; i < MAX_ARG_PAGES ; i++) {
Index: mm4-2.6.8.1/arch/ia64/kernel/perfmon.c
===================================================================
--- mm4-2.6.8.1.orig/arch/ia64/kernel/perfmon.c 2004-08-14 03:56:22.000000000 -0700
+++ mm4-2.6.8.1/arch/ia64/kernel/perfmon.c 2004-08-23 23:38:30.710068776 -0700
@@ -2352,7 +2352,7 @@
insert_vm_struct(mm, vma);

mm->total_vm += size >> PAGE_SHIFT;
-
+ vm_stat_account(vma);
up_write(&task->mm->mmap_sem);

/*
Index: mm4-2.6.8.1/arch/ia64/mm/fault.c
===================================================================
--- mm4-2.6.8.1.orig/arch/ia64/mm/fault.c 2004-08-23 16:10:56.000000000 -0700
+++ mm4-2.6.8.1/arch/ia64/mm/fault.c 2004-08-23 23:39:35.187266752 -0700
@@ -41,6 +41,7 @@
vma->vm_mm->total_vm += grow;
if (vma->vm_flags & VM_LOCKED)
vma->vm_mm->locked_vm += grow;
+ __vm_stat_account(vma->vm_mm, vma->vm_flags, vma->vm_file, grow);
return 0;
}

Index: mm4-2.6.8.1/arch/s390/kernel/compat_exec.c
===================================================================
--- mm4-2.6.8.1.orig/arch/s390/kernel/compat_exec.c 2004-08-14 03:56:01.000000000 -0700
+++ mm4-2.6.8.1/arch/s390/kernel/compat_exec.c 2004-08-23 23:30:04.183072584 -0700
@@ -69,7 +69,7 @@
mpnt->vm_page_prot = PAGE_COPY;
mpnt->vm_flags = VM_STACK_FLAGS;
insert_vm_struct(mm, mpnt);
- mm->total_vm = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
+ mm->stack_vm = mm->total_vm = vma_pages(mpnt);
}

for (i = 0 ; i < MAX_ARG_PAGES ; i++) {
Index: mm4-2.6.8.1/arch/x86_64/ia32/ia32_binfmt.c
===================================================================
--- mm4-2.6.8.1.orig/arch/x86_64/ia32/ia32_binfmt.c 2004-08-23 16:11:09.000000000 -0700
+++ mm4-2.6.8.1/arch/x86_64/ia32/ia32_binfmt.c 2004-08-23 23:28:07.283843968 -0700
@@ -368,7 +368,7 @@
mpnt->vm_page_prot = (mpnt->vm_flags & VM_EXEC) ?
PAGE_COPY_EXEC : PAGE_COPY;
insert_vm_struct(mm, mpnt);
- mm->total_vm = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
+ mm->stack_vm = mm->total_vm = vma_pages(mpnt);
}

for (i = 0 ; i < MAX_ARG_PAGES ; i++) {
Index: mm4-2.6.8.1/fs/exec.c
===================================================================
--- mm4-2.6.8.1.orig/fs/exec.c 2004-08-23 16:11:15.000000000 -0700
+++ mm4-2.6.8.1/fs/exec.c 2004-08-23 18:29:33.000000000 -0700
@@ -434,7 +434,7 @@
mpnt->vm_flags |= mm->def_flags;
mpnt->vm_page_prot = protection_map[mpnt->vm_flags & 0x7];
insert_vm_struct(mm, mpnt);
- mm->total_vm = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
+ mm->stack_vm = mm->total_vm = vma_pages(mpnt);
}

for (i = 0 ; i < MAX_ARG_PAGES ; i++) {
Index: mm4-2.6.8.1/fs/proc/array.c
===================================================================
--- mm4-2.6.8.1.orig/fs/proc/array.c 2004-08-23 18:29:08.000000000 -0700
+++ mm4-2.6.8.1/fs/proc/array.c 2004-08-23 20:23:43.000000000 -0700
@@ -279,7 +279,6 @@
cap_t(p->cap_effective));
}

-extern char *task_mem(struct mm_struct *, char *);
int proc_pid_status(struct task_struct *task, char * buffer)
{
char * orig = buffer;
@@ -415,17 +414,13 @@
return res;
}

-extern int task_statm(struct mm_struct *, int *, int *, int *, int *);
int proc_pid_statm(struct task_struct *task, char *buffer)
{
int size = 0, resident = 0, shared = 0, text = 0, lib = 0, data = 0;
struct mm_struct *mm = get_task_mm(task);

if (mm) {
- down_read(&mm->mmap_sem);
size = task_statm(mm, &shared, &text, &data, &resident);
- up_read(&mm->mmap_sem);
-
mmput(mm);
}

Index: mm4-2.6.8.1/fs/proc/task_mmu.c
===================================================================
--- mm4-2.6.8.1.orig/fs/proc/task_mmu.c 2004-08-14 03:54:50.000000000 -0700
+++ mm4-2.6.8.1/fs/proc/task_mmu.c 2004-08-23 18:29:33.000000000 -0700
@@ -6,27 +6,11 @@

char *task_mem(struct mm_struct *mm, char *buffer)
{
- unsigned long data = 0, stack = 0, exec = 0, lib = 0;
- struct vm_area_struct *vma;
+ unsigned long data, text, lib;

- down_read(&mm->mmap_sem);
- for (vma = mm->mmap; vma; vma = vma->vm_next) {
- unsigned long len = (vma->vm_end - vma->vm_start) >> 10;
- if (!vma->vm_file) {
- data += len;
- if (vma->vm_flags & VM_GROWSDOWN)
- stack += len;
- continue;
- }
- if (vma->vm_flags & VM_WRITE)
- continue;
- if (vma->vm_flags & VM_EXEC) {
- exec += len;
- if (vma->vm_flags & VM_EXECUTABLE)
- continue;
- lib += len;
- }
- }
+ data = mm->total_vm - mm->shared_vm - mm->stack_vm;
+ text = (mm->end_code - mm->start_code) >> 10;
+ lib = (mm->exec_vm << (PAGE_SHIFT-10)) - text;
buffer += sprintf(buffer,
"VmSize:\t%8lu kB\n"
"VmLck:\t%8lu kB\n"
@@ -38,9 +22,8 @@
mm->total_vm << (PAGE_SHIFT-10),
mm->locked_vm << (PAGE_SHIFT-10),
mm->rss << (PAGE_SHIFT-10),
- data - stack, stack,
- exec - lib, lib);
- up_read(&mm->mmap_sem);
+ data << (PAGE_SHIFT-10),
+ mm->stack_vm << (PAGE_SHIFT-10), text, lib);
return buffer;
}

@@ -52,28 +35,11 @@
int task_statm(struct mm_struct *mm, int *shared, int *text,
int *data, int *resident)
{
- struct vm_area_struct *vma;
- int size = 0;
-
+ *shared = mm->shared_vm;
+ *text = mm->exec_vm - ((mm->end_code - mm->start_code) >> PAGE_SHIFT);
+ *data = mm->total_vm - mm->shared_vm;
*resident = mm->rss;
- for (vma = mm->mmap; vma; vma = vma->vm_next) {
- int pages = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
-
- size += pages;
- if (is_vm_hugetlb_page(vma)) {
- if (!(vma->vm_flags & VM_DONTCOPY))
- *shared += pages;
- continue;
- }
- if (vma->vm_file)
- *shared += pages;
- if (vma->vm_flags & VM_EXECUTABLE)
- *text += pages;
- else
- *data += pages;
- }
-
- return size;
+ return mm->total_vm;
}

static int show_map(struct seq_file *m, void *v)
Index: mm4-2.6.8.1/fs/proc/task_nommu.c
===================================================================
--- mm4-2.6.8.1.orig/fs/proc/task_nommu.c 2004-08-23 18:29:08.000000000 -0700
+++ mm4-2.6.8.1/fs/proc/task_nommu.c 2004-08-23 18:29:33.000000000 -0700
@@ -82,7 +82,8 @@
{
struct mm_tblock_struct *tbp;
int size = kobjsize(mm);
-
+
+ down_read(&mm->mmap_sem);
for (tbp = &mm->context.tblock; tbp; tbp = tbp->next) {
if (tbp->next)
size += kobjsize(tbp->next);
@@ -94,7 +95,7 @@

size += (*text = mm->end_code - mm->start_code);
size += (*data = mm->start_stack - mm->start_data);
-
+ up_read(&mm->mmap_sem);
*resident = size;
return size;
}
Index: mm4-2.6.8.1/include/linux/mm.h
===================================================================
--- mm4-2.6.8.1.orig/include/linux/mm.h 2004-08-23 16:11:19.000000000 -0700
+++ mm4-2.6.8.1/include/linux/mm.h 2004-08-23 18:29:33.000000000 -0700
@@ -754,6 +754,19 @@
int write);
extern int remap_page_range(struct vm_area_struct *vma, unsigned long from,
unsigned long to, unsigned long size, pgprot_t prot);
+void __vm_stat_account(struct mm_struct *, unsigned long, struct file *, long);
+
+static inline void vm_stat_account(struct vm_area_struct *vma)
+{
+ __vm_stat_account(vma->vm_mm, vma->vm_flags, vma->vm_file,
+ vma_pages(vma));
+}
+
+static inline void vm_stat_unaccount(struct vm_area_struct *vma)
+{
+ __vm_stat_account(vma->vm_mm, vma->vm_flags, vma->vm_file,
+ -vma_pages(vma));
+}

#ifndef CONFIG_DEBUG_PAGEALLOC
static inline void
Index: mm4-2.6.8.1/include/linux/proc_fs.h
===================================================================
--- mm4-2.6.8.1.orig/include/linux/proc_fs.h 2004-08-23 20:23:29.000000000 -0700
+++ mm4-2.6.8.1/include/linux/proc_fs.h 2004-08-23 20:23:43.000000000 -0700
@@ -91,6 +91,8 @@
void proc_pid_flush(struct dentry *proc_dentry);
int proc_pid_readdir(struct file * filp, void * dirent, filldir_t filldir);
unsigned long task_vsize(struct mm_struct *);
+int task_statm(struct mm_struct *, int *, int *, int *, int *);
+char *task_mem(struct mm_struct *, char *);

extern struct proc_dir_entry *create_proc_entry(const char *name, mode_t mode,
struct proc_dir_entry *parent);
Index: mm4-2.6.8.1/include/linux/sched.h
===================================================================
--- mm4-2.6.8.1.orig/include/linux/sched.h 2004-08-23 16:11:20.000000000 -0700
+++ mm4-2.6.8.1/include/linux/sched.h 2004-08-23 18:29:33.000000000 -0700
@@ -225,8 +225,8 @@
unsigned long start_code, end_code, start_data, end_data;
unsigned long start_brk, brk, start_stack;
unsigned long arg_start, arg_end, env_start, env_end;
- unsigned long rlimit_rss, rss, total_vm, locked_vm;
- unsigned long def_flags;
+ unsigned long rlimit_rss, rss, total_vm, locked_vm, shared_vm;
+ unsigned long exec_vm, stack_vm, def_flags;

unsigned long saved_auxv[40]; /* for /proc/PID/auxv */

Index: mm4-2.6.8.1/mm/mmap.c
===================================================================
--- mm4-2.6.8.1.orig/mm/mmap.c 2004-08-23 16:11:20.000000000 -0700
+++ mm4-2.6.8.1/mm/mmap.c 2004-08-23 23:33:42.411896760 -0700
@@ -729,6 +729,28 @@
return NULL;
}

+void __vm_stat_account(struct mm_struct *mm, unsigned long flags,
+ struct file *file, long pages)
+{
+ const unsigned long stack_flags
+ = VM_STACK_FLAGS & (VM_GROWSUP|VM_GROWSDOWN);
+
+#ifdef CONFIG_HUGETLB
+ if (flags & VM_HUGETLB) {
+ if (!(flags & VM_DONTCOPY))
+ mm->shared_vm += pages;
+ return;
+ }
+#endif /* CONFIG_HUGETLB */
+
+ if (file)
+ mm->shared_vm += pages;
+ else if (flags & stack_flags)
+ mm->stack_vm += pages;
+ if (flags & VM_EXEC)
+ mm->exec_vm += pages;
+}
+
/*
* The caller must hold down_write(current->mm->mmap_sem).
*/
@@ -987,6 +1009,7 @@
pgoff, flags & MAP_NONBLOCK);
down_write(&mm->mmap_sem);
}
+ __vm_stat_account(mm, vm_flags, file, len >> PAGE_SHIFT);
return addr;

unmap_and_free_vma:
@@ -1330,6 +1353,7 @@
vma->vm_mm->total_vm += grow;
if (vma->vm_flags & VM_LOCKED)
vma->vm_mm->locked_vm += grow;
+ __vm_stat_account(vma->vm_mm, vma->vm_flags, vma->vm_file, grow);
anon_vma_unlock(vma);
return 0;
}
@@ -1392,6 +1416,7 @@
vma->vm_mm->total_vm += grow;
if (vma->vm_flags & VM_LOCKED)
vma->vm_mm->locked_vm += grow;
+ __vm_stat_account(vma->vm_mm, vma->vm_flags, vma->vm_file, grow);
anon_vma_unlock(vma);
return 0;
}
@@ -1497,6 +1522,7 @@
area->vm_mm->total_vm -= len >> PAGE_SHIFT;
if (area->vm_flags & VM_LOCKED)
area->vm_mm->locked_vm -= len >> PAGE_SHIFT;
+ vm_stat_unaccount(area);
area->vm_mm->unmap_area(area);
remove_vm_struct(area);
}
Index: mm4-2.6.8.1/mm/mprotect.c
===================================================================
--- mm4-2.6.8.1.orig/mm/mprotect.c 2004-08-14 03:56:26.000000000 -0700
+++ mm4-2.6.8.1/mm/mprotect.c 2004-08-23 18:29:33.000000000 -0700
@@ -175,9 +175,11 @@
* vm_flags and vm_page_prot are protected by the mmap_sem
* held in write mode.
*/
+ vm_stat_unaccount(vma);
vma->vm_flags = newflags;
vma->vm_page_prot = newprot;
change_protection(vma, start, end, newprot);
+ vm_stat_account(vma);
return 0;

fail:
Index: mm4-2.6.8.1/mm/mremap.c
===================================================================
--- mm4-2.6.8.1.orig/mm/mremap.c 2004-08-23 16:11:13.000000000 -0700
+++ mm4-2.6.8.1/mm/mremap.c 2004-08-24 00:01:28.808565960 -0700
@@ -224,6 +224,7 @@
}

mm->total_vm += new_len >> PAGE_SHIFT;
+ __vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT);
if (vm_flags & VM_LOCKED) {
mm->locked_vm += new_len >> PAGE_SHIFT;
if (new_len > old_len)
@@ -360,6 +361,8 @@
addr + new_len, vma->vm_pgoff, NULL);

current->mm->total_vm += pages;
+ __vm_stat_account(vma->vm_mm, vma->vm_flags,
+ vma->vm_file, pages);
if (vma->vm_flags & VM_LOCKED) {
current->mm->locked_vm += pages;
make_pages_present(addr + old_len,
-
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