mm: introduce get_mm_hiwater_xxx(), fix taskstats->hiwater_xxx accounting (901608d9) · Commits · 戴 / test

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>

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);

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