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mm: introduce get_mm_hiwater_xxx(), fix taskstats->hiwater_xxx accounting

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xacct_add_tsk() relies on do_exit()->update_hiwater_xxx() and uses
mm->hiwater_xxx directly, this leads to 2 problems:

- taskstats_user_cmd() can call fill_pid()->xacct_add_tsk() at any
  moment before the task exits, so we should check the current values of
  rss/vm anyway.

- do_exit()->update_hiwater_xxx() calls are racy.  An exiting thread can
  be preempted right before mm->hiwater_xxx = new_val, and another thread
  can use A_LOT of memory and exit in between.  When the first thread
  resumes it can be the last thread in the thread group, in that case we
  report the wrong hiwater_xxx values which do not take A_LOT into
  account.

Introduce get_mm_hiwater_rss() and get_mm_hiwater_vm() helpers and change
xacct_add_tsk() to use them.  The first helper will also be used by
rusage->ru_maxrss accounting.

Kill do_exit()->update_hiwater_xxx() calls.  Unless we are going to
decrease rss/vm there is no point to update mm->hiwater_xxx, and nobody
can look at this mm_struct when exit_mmap() actually unmaps the memory.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Hugh Dickins <hugh@veritas.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Oleg Nesterov 2009-01-06 14:40:29 -08:00 committed by Linus Torvalds
parent 67d58ac47d
commit 901608d904
4 changed files with 7 additions and 7 deletions
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3
include/linux/sched.h
View file

@ -386,6 +386,9 @@ extern void arch_unmap_area_topdown(struct mm_struct *, unsigned long);
(mm)->hiwater_vm = (mm)->total_vm; \
} while (0)
#define get_mm_hiwater_rss(mm) max((mm)->hiwater_rss, get_mm_rss(mm))
#define get_mm_hiwater_vm(mm) max((mm)->hiwater_vm, (mm)->total_vm)
extern void set_dumpable(struct mm_struct *mm, int value);
extern int get_dumpable(struct mm_struct *mm);

5
kernel/exit.c
View file

@ -1051,10 +1051,7 @@ NORET_TYPE void do_exit(long code)
preempt_count());
acct_update_integrals(tsk);
if (tsk->mm) {
update_hiwater_rss(tsk->mm);
update_hiwater_vm(tsk->mm);
}
group_dead = atomic_dec_and_test(&tsk->signal->live);
if (group_dead) {
hrtimer_cancel(&tsk->signal->real_timer);

4
kernel/tsacct.c
View file

@ -92,8 +92,8 @@ void xacct_add_tsk(struct taskstats *stats, struct task_struct *p)
mm = get_task_mm(p);
if (mm) {
/* adjust to KB unit */
stats->hiwater_rss = mm->hiwater_rss * PAGE_SIZE / KB;
stats->hiwater_vm = mm->hiwater_vm * PAGE_SIZE / KB;
stats->hiwater_rss = get_mm_hiwater_rss(mm) * PAGE_SIZE / KB;
stats->hiwater_vm = get_mm_hiwater_vm(mm) * PAGE_SIZE / KB;
mmput(mm);
}
stats->read_char = p->ioac.rchar;

2
mm/mmap.c
View file

@ -2102,7 +2102,7 @@ void exit_mmap(struct mm_struct *mm)
lru_add_drain();
flush_cache_mm(mm);
tlb = tlb_gather_mmu(mm, 1);
/* Don't update_hiwater_rss(mm) here, do_exit already did */
/* update_hiwater_rss(mm) here? but nobody should be looking */
/* Use -1 here to ensure all VMAs in the mm are unmapped */
end = unmap_vmas(&tlb, vma, 0, -1, &nr_accounted, NULL);
vm_unacct_memory(nr_accounted);