From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it0-f71.google.com (mail-it0-f71.google.com [209.85.214.71]) by kanga.kvack.org (Postfix) with ESMTP id BD5F26B0261 for ; Tue, 12 Jul 2016 09:30:15 -0400 (EDT) Received: by mail-it0-f71.google.com with SMTP id f6so30154101ith.3 for ; Tue, 12 Jul 2016 06:30:15 -0700 (PDT) Received: from www262.sakura.ne.jp (www262.sakura.ne.jp. [2001:e42:101:1:202:181:97:72]) by mx.google.com with ESMTPS id e85si432532oig.147.2016.07.12.06.30.13 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 12 Jul 2016 06:30:14 -0700 (PDT) From: Tetsuo Handa Subject: [PATCH 1/8] mm,oom_reaper: Reduce find_lock_task_mm() usage. Date: Tue, 12 Jul 2016 22:29:16 +0900 Message-Id: <1468330163-4405-2-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> In-Reply-To: <1468330163-4405-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> References: <1468330163-4405-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> Sender: owner-linux-mm@kvack.org List-ID: To: mhocko@suse.com, mhocko@kernel.org Cc: akpm@linux-foundation.org, linux-mm@kvack.org, oleg@redhat.com, rientjes@google.com, vdavydov@parallels.com, mst@redhat.com, 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 Acked-by: Michal Hocko --- mm/oom_kill.c | 79 ++++++++++++++++++++++++++++------------------------------- 1 file changed, 37 insertions(+), 42 deletions(-) diff --git a/mm/oom_kill.c b/mm/oom_kill.c index 7d0a275..951eb1b 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -452,12 +452,10 @@ 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(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; @@ -478,22 +476,9 @@ 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; } /* @@ -503,7 +488,7 @@ 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); @@ -551,8 +536,6 @@ 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; @@ -562,36 +545,45 @@ unlock_oom: 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(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 @@ -603,6 +595,9 @@ 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) -- 1.8.3.1 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org