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Patch series "Improvements to Victim Process Thawing and OOM Reaper Traversal Order", v10. This patch series focuses on optimizing victim process thawing and refining the traversal order of the OOM reaper. Since __thaw_task() is used to thaw a single thread of the victim, thawing only one thread cannot guarantee the exit of the OOM victim when it is frozen. Patch 1 thaw the entire process of the OOM victim to ensure that OOM victims are able to terminate themselves. Even if the oom_reaper is delayed, patch 2 is still beneficial for reaping processes with a large address space footprint, and it also greatly improves process_mrelease. This patch (of 10): OOM killer is a mechanism that selects and kills processes when the system runs out of memory to reclaim resources and keep the system stable. But the oom victim cannot terminate on its own when it is frozen, even if the OOM victim task is thawed through __thaw_task(). This is because __thaw_task() can only thaw a single OOM victim thread, and cannot thaw the entire OOM victim process. In addition, freezing_slow_path() determines whether a task is an OOM victim by checking the task's TIF_MEMDIE flag. When a task is identified as an OOM victim, the freezer bypasses both PM freezing and cgroup freezing states to thaw it. Historically, TIF_MEMDIE was a "this is the oom victim & it has access to memory reserves" flag in the past. It has that thread vs. process problems and tsk_is_oom_victim was introduced later to get rid of them and other issues as well as the guarantee that we can identify the oom victim's mm reliably for other oom_reaper. Therefore, thaw_process() is introduced to unfreeze all threads within the OOM victim process, ensuring that every thread is properly thawed. The freezer now uses tsk_is_oom_victim() to determine OOM victim status, allowing all victim threads to be unfrozen as necessary. With this change, the entire OOM victim process will be thawed when an OOM event occurs, ensuring that the victim can terminate on its own. Link: https://lkml.kernel.org/r/20250915162946.5515-1-zhongjinji@honor.com Link: https://lkml.kernel.org/r/20250915162946.5515-2-zhongjinji@honor.com Signed-off-by: zhongjinji <zhongjinji@honor.com> Reviewed-by: Suren Baghdasaryan <surenb@google.com> Acked-by: Shakeel Butt <shakeel.butt@linux.dev> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Liam R. Howlett <Liam.Howlett@oracle.com> Cc: David Rientjes <rientjes@google.com> Cc: Len Brown <lenb@kernel.org> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Thomas Gleinxer <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
93 lines
2.4 KiB
C
93 lines
2.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/* Freezer declarations */
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#ifndef FREEZER_H_INCLUDED
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#define FREEZER_H_INCLUDED
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#include <linux/debug_locks.h>
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#include <linux/sched.h>
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#include <linux/wait.h>
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#include <linux/atomic.h>
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#include <linux/jump_label.h>
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#ifdef CONFIG_FREEZER
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DECLARE_STATIC_KEY_FALSE(freezer_active);
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extern bool pm_freezing; /* PM freezing in effect */
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extern bool pm_nosig_freezing; /* PM nosig freezing in effect */
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/*
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* Timeout for stopping processes
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*/
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extern unsigned int freeze_timeout_msecs;
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/*
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* Check if a process has been frozen
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*/
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extern bool frozen(struct task_struct *p);
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extern bool freezing_slow_path(struct task_struct *p);
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/*
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* Check if there is a request to freeze a process
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*/
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static inline bool freezing(struct task_struct *p)
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{
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if (static_branch_unlikely(&freezer_active))
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return freezing_slow_path(p);
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return false;
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}
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/* Takes and releases task alloc lock using task_lock() */
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extern void __thaw_task(struct task_struct *t);
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extern bool __refrigerator(bool check_kthr_stop);
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extern int freeze_processes(void);
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extern int freeze_kernel_threads(void);
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extern void thaw_processes(void);
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extern void thaw_kernel_threads(void);
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extern void thaw_process(struct task_struct *p);
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static inline bool try_to_freeze(void)
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{
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might_sleep();
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if (likely(!freezing(current)))
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return false;
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if (!(current->flags & PF_NOFREEZE))
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debug_check_no_locks_held();
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return __refrigerator(false);
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}
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extern bool freeze_task(struct task_struct *p);
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extern bool set_freezable(void);
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#ifdef CONFIG_CGROUP_FREEZER
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extern bool cgroup_freezing(struct task_struct *task);
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#else /* !CONFIG_CGROUP_FREEZER */
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static inline bool cgroup_freezing(struct task_struct *task)
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{
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return false;
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}
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#endif /* !CONFIG_CGROUP_FREEZER */
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#else /* !CONFIG_FREEZER */
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static inline bool frozen(struct task_struct *p) { return false; }
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static inline bool freezing(struct task_struct *p) { return false; }
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static inline void __thaw_task(struct task_struct *t) {}
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static inline bool __refrigerator(bool check_kthr_stop) { return false; }
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static inline int freeze_processes(void) { return -ENOSYS; }
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static inline int freeze_kernel_threads(void) { return -ENOSYS; }
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static inline void thaw_processes(void) {}
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static inline void thaw_kernel_threads(void) {}
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static inline void thaw_process(struct task_struct *p) {}
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static inline bool try_to_freeze(void) { return false; }
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static inline void set_freezable(void) {}
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#endif /* !CONFIG_FREEZER */
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#endif /* FREEZER_H_INCLUDED */
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