Messages in this thread Patch in this message | | | Date | Fri, 12 Dec 2008 15:05:24 +0100 | From | Oleg Nesterov <> | Subject | [PATCH, RESEND] introduce get_mm_hiwater_xxx(), fix taskstats->hiwater_xxx accounting |
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(changes: update the changelog/comments)
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>
--- K-28/include/linux/sched.h~HIWATER 2008-12-02 17:12:40.000000000 +0100 +++ K-28/include/linux/sched.h 2008-12-03 18:17:18.000000000 +0100 @@ -388,6 +388,9 @@ extern void arch_unmap_area_topdown(stru (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); --- K-28/kernel/tsacct.c~HIWATER 2008-10-10 00:13:53.000000000 +0200 +++ K-28/kernel/tsacct.c 2008-12-03 18:24:28.000000000 +0100 @@ -90,8 +90,8 @@ void xacct_add_tsk(struct taskstats *sta 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; --- K-28/kernel/exit.c~HIWATER 2008-12-02 17:12:40.000000000 +0100 +++ K-28/kernel/exit.c 2008-12-03 18:21:06.000000000 +0100 @@ -1048,10 +1048,7 @@ 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); --- K-28/mm/mmap.c~HIWATER 2008-12-02 17:12:40.000000000 +0100 +++ K-28/mm/mmap.c 2008-12-11 09:13:07.000000000 +0100 @@ -2103,7 +2103,7 @@ 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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