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Commit 901608d9 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
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mm: introduce get_mm_hiwater_xxx(), fix taskstats->hiwater_xxx accounting 



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: default avatarOleg Nesterov <oleg@redhat.com>
Acked-by: default avatarHugh Dickins <hugh@veritas.com>
Reviewed-by: default avatarKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: default avatarBalbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 67d58ac4

include/linux/sched.h

+3 −0
Original line number Diff line number Diff line
@@ -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);

kernel/exit.c

+1 −4
Original line number Diff line number Diff line
@@ -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);

kernel/tsacct.c

+2 −2
Original line number Diff line number Diff line
@@ -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;

mm/mmap.c

+1 −1
Original line number Diff line number Diff line
@@ -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);