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From: Shakeel Butt To: zhongjinji Cc: mhocko@suse.com, rientjes@google.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, liam.howlett@oracle.com, lorenzo.stoakes@oracle.com, liulu.liu@honor.com, feng.han@honor.com, cgroups@vger.kernel.org Subject: Re: [PATCH v5 1/2] mm/oom_kill: Do not delay oom reaper when the victim is frozen Message-ID: References: <20250825133855.30229-1-zhongjinji@honor.com> <20250825133855.30229-2-zhongjinji@honor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250825133855.30229-2-zhongjinji@honor.com> X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: 49B53140005 X-Rspam-User: X-Stat-Signature: 46hp7nk673jf8c4schxmdg3x3hu9yhau X-Rspamd-Server: rspam09 X-HE-Tag: 1756150876-486311 X-HE-Meta: U2FsdGVkX1/5zTM7CTDSsQginPe11mACGtZw32oJIjtCjO3B24Cnq7IWOfVeYz4yToiSv8zdD3PL1nuMiT+I5NGJn8Q1+bQVPdCd+CaHZ1xbPhx7nmhOUXTN3yE+w8zRyp7A1hQtwzpWVWSTRsTR3niJ5jEDqutCvSDzVrFMtlRF310SyTc4bnMp7MxLzzhmf5jhodMf2/B7sTNs2YdQAMvNUssoMUiu6jYGOMiRfACPuOkWcQoZc3+vD9wv2Y6CByfO/WWoH3RPcXtP5WyuQsrx756qDyXoODNIBu/cERNczdOPMhOLlIjht59ZSSUasJbQctLeYkVGod5LslGSa+tO15LEHYriAIexESmU1eQf/G8QHLVTY1vdkA7xICKxbN5WUvs+HoKz0FYVSw1ofs3bfa/wDwMLWjQ3aTl5uesR3hfbs/ot3cw5RkurTIjZKe89T1cffuw5KI86KkR5IPrfCWjXeOzcLvG4jfWUac+omkvLBdbcTVz9qrDMvCw18FzweFH4cbbVrJUxNi3hx/TMa3xh1/3ydBweHKKQa543FBdT/KWWm67eGh9yUK6vFtTU/+Yr64110M9abmpXE83Aregmg537uC37Exe6nkxgqTDn1i5dTdEmk7jmQli28f4xCbJSpZV6RGhT3v7bxT7ePrFTsOr4YApf3jenlOiPDmhrMG2jnOUgJWrYD7KhTNpElu9SEXbukYVmEWvZaDcX3ZbM4YhdjzfcEBLlbj+0wpI6sijWiA7LIUSngzunETu1k5aWneYyuxgOM85AoKDl8HgVa5JdeW4IbTGFPl5Aq3VE3mZMJzVz1f+rwJJ7anv4CH4J7qG6Vwxl0OUyW/XFUE3ddWv1O7Jm5WQOIyGIBkwp44ll9DrUrHZFf5Cr1DVunplgtwav86tqtSTIm+yBl/t6iV7EQ68iDEuvjmolXThlTyDRlw1R0Ec6u8yxAAaeJaruR7P23WJ2DS6 vA0VMSag AuhxWAEIS2e41PBhAMDA1eQ2JSjWv1Urm8fJbh5CvdGheg7Rv5nRlUHrO3oOBg12uKbmtpn5Q7uv0I2mWGZdaMCjURbjcjRbOl5OXwDp5v2X7SQFc4cQvshaKQrzKAYBNWeWxygsTOVMLUH7O7cp7ndS/zVdkXQAGm7aB+jK+xJp+PuCSTzckUAwUE67GaeSKdNGPyMv7fBI8jVC6X90Z8nV8h75YiGpuONe+6khbqtJAB3f00T3Te4uCCPfmuuV+cxsRShLjoAoKde1ws0NDGR9/PFnMDIeXd//h2P/axsKuvbooXIaa4zeGLajclKF0VlTUCHQJyv5U2URVGXDCe9K6arFYBF6Crrg3JX/zLJQyAdSKBZVnw/dGS/wKbUSfSysL X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: +cgroups On Mon, Aug 25, 2025 at 09:38:54PM +0800, zhongjinji wrote: > The OOM reaper can quickly reap a process's memory when the system > encounters OOM, helping the system recover. If the victim process is > frozen and cannot be unfrozen in time, the reaper delayed by two seconds > will cause the system to fail to recover quickly from the OOM state. > > When an OOM occurs, if the victim is not unfrozen, delaying the OOM reaper > will keep the system in a bad state for two seconds. Before scheduling the > oom_reaper task, check whether the victim is in a frozen state. If the > victim is frozen, do not delay the OOM reaper. > > Signed-off-by: zhongjinji > --- > mm/oom_kill.c | 40 +++++++++++++++++++++++++++++++++++++++- > 1 file changed, 39 insertions(+), 1 deletion(-) > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > index 25923cfec9c6..4b4d73b1e00d 100644 > --- a/mm/oom_kill.c > +++ b/mm/oom_kill.c > @@ -683,6 +683,41 @@ static void wake_oom_reaper(struct timer_list *timer) > wake_up(&oom_reaper_wait); > } > > +/* > + * When the victim is frozen, the OOM reaper should not be delayed, because > + * if the victim cannot be unfrozen promptly, it may block the system from > + * quickly recovering from the OOM state. > + */ > +static bool should_delay_oom_reap(struct task_struct *tsk) > +{ > + struct mm_struct *mm = tsk->mm; > + struct task_struct *p; > + bool ret; > + On v2, shouldn't READ_ONCE(tsk->frozen) be enough instead of mm check and checks insode for_each_process()? > + if (!mm) > + return true; > + > + if (!frozen(tsk)) > + return true; > + > + if (atomic_read(&mm->mm_users) <= 1) > + return false; > + > + rcu_read_lock(); > + for_each_process(p) { > + if (!process_shares_mm(p, mm)) > + continue; > + if (same_thread_group(tsk, p)) > + continue; > + ret = !frozen(p); > + if (ret) > + break; > + } > + rcu_read_unlock(); > + > + return ret; > +} > + > /* > * Give the OOM victim time to exit naturally before invoking the oom_reaping. > * The timers timeout is arbitrary... the longer it is, the longer the worst > @@ -694,13 +729,16 @@ static void wake_oom_reaper(struct timer_list *timer) > #define OOM_REAPER_DELAY (2*HZ) > static void queue_oom_reaper(struct task_struct *tsk) > { > + bool delay; > + > /* mm is already queued? */ > if (test_and_set_bit(MMF_OOM_REAP_QUEUED, &tsk->signal->oom_mm->flags)) > return; > > get_task_struct(tsk); > + delay = should_delay_oom_reap(tsk); > timer_setup(&tsk->oom_reaper_timer, wake_oom_reaper, 0); > - tsk->oom_reaper_timer.expires = jiffies + OOM_REAPER_DELAY; > + tsk->oom_reaper_timer.expires = jiffies + (delay ? OOM_REAPER_DELAY : 0); > add_timer(&tsk->oom_reaper_timer); > } > > -- > 2.17.1 >