From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-f69.google.com (mail-lf0-f69.google.com [209.85.215.69]) by kanga.kvack.org (Postfix) with ESMTP id 020FB83093 for ; Thu, 25 Aug 2016 06:03:30 -0400 (EDT) Received: by mail-lf0-f69.google.com with SMTP id p85so28650620lfg.3 for ; Thu, 25 Aug 2016 03:03:29 -0700 (PDT) Received: from mail-wm0-f65.google.com (mail-wm0-f65.google.com. [74.125.82.65]) by mx.google.com with ESMTPS id m68si13528200wma.37.2016.08.25.03.03.28 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 25 Aug 2016 03:03:28 -0700 (PDT) Received: by mail-wm0-f65.google.com with SMTP id i5so6652288wmg.2 for ; Thu, 25 Aug 2016 03:03:28 -0700 (PDT) From: Michal Hocko Subject: [PATCH v2 1/9] mm,oom_reaper: Reduce find_lock_task_mm() usage. Date: Thu, 25 Aug 2016 12:03:06 +0200 Message-Id: <1472119394-11342-2-git-send-email-mhocko@kernel.org> In-Reply-To: <1472119394-11342-1-git-send-email-mhocko@kernel.org> References: <1472119394-11342-1-git-send-email-mhocko@kernel.org> Sender: owner-linux-mm@kvack.org List-ID: To: linux-mm@kvack.org Cc: Andrew Morton , Tetsuo Handa , Oleg Nesterov , David Rientjes , Vladimir Davydov , Michal Hocko From: Tetsuo Handa __oom_reap_task() can be simplified a bit if it receives a valid mm from oom_reap_task() which also uses that mm when __oom_reap_task() failed. We can drop one find_lock_task_mm() call and also make the __oom_reap_task() code flow easier to follow. Moreover, this will make later patch in the series easier to review. Pinning mm's mm_count for longer time is not really harmful because this will not pin much memory. This patch doesn't introduce any functional change. Signed-off-by: Tetsuo Handa Signed-off-by: Michal Hocko --- mm/oom_kill.c | 81 ++++++++++++++++++++++++++++------------------------------- 1 file changed, 38 insertions(+), 43 deletions(-) diff --git a/mm/oom_kill.c b/mm/oom_kill.c index 463cdd22d4e0..87fad956c96b 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -463,12 +463,10 @@ static DECLARE_WAIT_QUEUE_HEAD(oom_reaper_wait); static struct task_struct *oom_reaper_list; static DEFINE_SPINLOCK(oom_reaper_lock); -static bool __oom_reap_task(struct task_struct *tsk) +static bool __oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm) { struct mmu_gather tlb; struct vm_area_struct *vma; - struct mm_struct *mm = NULL; - struct task_struct *p; struct zap_details details = {.check_swap_entries = true, .ignore_dirty = true}; bool ret = true; @@ -476,7 +474,7 @@ static bool __oom_reap_task(struct task_struct *tsk) /* * We have to make sure to not race with the victim exit path * and cause premature new oom victim selection: - * __oom_reap_task exit_mm + * __oom_reap_task_mm exit_mm * mmget_not_zero * mmput * atomic_dec_and_test @@ -489,22 +487,9 @@ static bool __oom_reap_task(struct task_struct *tsk) */ mutex_lock(&oom_lock); - /* - * Make sure we find the associated mm_struct even when the particular - * thread has already terminated and cleared its mm. - * We might have race with exit path so consider our work done if there - * is no mm. - */ - p = find_lock_task_mm(tsk); - if (!p) - goto unlock_oom; - mm = p->mm; - atomic_inc(&mm->mm_count); - task_unlock(p); - if (!down_read_trylock(&mm->mmap_sem)) { ret = false; - goto mm_drop; + goto unlock_oom; } /* @@ -514,7 +499,7 @@ static bool __oom_reap_task(struct task_struct *tsk) */ if (!mmget_not_zero(mm)) { up_read(&mm->mmap_sem); - goto mm_drop; + goto unlock_oom; } tlb_gather_mmu(&tlb, mm, 0, -1); @@ -562,8 +547,6 @@ static bool __oom_reap_task(struct task_struct *tsk) * put the oom_reaper out of the way. */ mmput_async(mm); -mm_drop: - mmdrop(mm); unlock_oom: mutex_unlock(&oom_lock); return ret; @@ -573,36 +556,45 @@ static bool __oom_reap_task(struct task_struct *tsk) static void oom_reap_task(struct task_struct *tsk) { int attempts = 0; + struct mm_struct *mm = NULL; + struct task_struct *p = find_lock_task_mm(tsk); + + /* + * Make sure we find the associated mm_struct even when the particular + * thread has already terminated and cleared its mm. + * We might have race with exit path so consider our work done if there + * is no mm. + */ + if (!p) + goto done; + mm = p->mm; + atomic_inc(&mm->mm_count); + task_unlock(p); /* Retry the down_read_trylock(mmap_sem) a few times */ - while (attempts++ < MAX_OOM_REAP_RETRIES && !__oom_reap_task(tsk)) + while (attempts++ < MAX_OOM_REAP_RETRIES && !__oom_reap_task_mm(tsk, mm)) schedule_timeout_idle(HZ/10); - if (attempts > MAX_OOM_REAP_RETRIES) { - struct task_struct *p; + if (attempts <= MAX_OOM_REAP_RETRIES) + goto done; - pr_info("oom_reaper: unable to reap pid:%d (%s)\n", - task_pid_nr(tsk), tsk->comm); + pr_info("oom_reaper: unable to reap pid:%d (%s)\n", + task_pid_nr(tsk), tsk->comm); - /* - * If we've already tried to reap this task in the past and - * failed it probably doesn't make much sense to try yet again - * so hide the mm from the oom killer so that it can move on - * to another task with a different mm struct. - */ - p = find_lock_task_mm(tsk); - if (p) { - if (test_and_set_bit(MMF_OOM_NOT_REAPABLE, &p->mm->flags)) { - pr_info("oom_reaper: giving up pid:%d (%s)\n", - task_pid_nr(tsk), tsk->comm); - set_bit(MMF_OOM_REAPED, &p->mm->flags); - } - task_unlock(p); - } - - debug_show_all_locks(); + /* + * If we've already tried to reap this task in the past and + * failed it probably doesn't make much sense to try yet again + * so hide the mm from the oom killer so that it can move on + * to another task with a different mm struct. + */ + if (test_and_set_bit(MMF_OOM_NOT_REAPABLE, &mm->flags)) { + pr_info("oom_reaper: giving up pid:%d (%s)\n", + task_pid_nr(tsk), tsk->comm); + set_bit(MMF_OOM_REAPED, &mm->flags); } + debug_show_all_locks(); +done: /* * Clear TIF_MEMDIE because the task shouldn't be sitting on a * reasonably reclaimable memory anymore or it is not a good candidate @@ -614,6 +606,9 @@ static void oom_reap_task(struct task_struct *tsk) /* Drop a reference taken by wake_oom_reaper */ put_task_struct(tsk); + /* Drop a reference taken above. */ + if (mm) + mmdrop(mm); } static int oom_reaper(void *unused) -- 2.8.1 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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