Messages in this thread Patch in this message | | | Date | Tue, 14 Jul 2009 17:52:28 -0700 | Subject | Re: + oom-move-oom_adj-value-from-task_struct-to-mm_struct.patch added to -mm tree | From | Paul Menage <> |
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On Mon, Jun 1, 2009 at 10:57 PM, <akpm@linux-foundation.org> wrote: > > The patch titled > oom: move oom_adj value from task_struct to mm_struct > has been added to the -mm tree. Its filename is > oom-move-oom_adj-value-from-task_struct-to-mm_struct.patch
This patch represents an API/semantics change that's invisible from userspace, unless userspace specifically checks for the old and new behaviours to see which applies.
Is it intentional that it's now impossible to create a tree of processes that will inherit a non-zero oom_adj? It appears to get reset whenever you exec a child process.
Old behaviour:
[root@localhost ~]# echo -1 > /proc/$$/oom_adj [root@localhost ~]# cat /proc/$$/oom_adj -1 [root@localhost ~]# bash [root@localhost ~]# cat /proc/$$/oom_adj -1
New behaviour:
[root@localhost ~]# echo -1 > /proc/$$/oom_adj [root@localhost ~]# cat /proc/$$/oom_adj -1 [root@localhost ~]# bash [root@localhost ~]# cat /proc/$$/oom_adj 0
> > Before you just go and hit "reply", please: > a) Consider who else should be cc'ed > b) Prefer to cc a suitable mailing list as well > c) Ideally: find the original patch on the mailing list and do a > reply-to-all to that, adding suitable additional cc's > > *** Remember to use Documentation/SubmitChecklist when testing your code *** > > See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find > out what to do about this > > The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ > > ------------------------------------------------------ > Subject: oom: move oom_adj value from task_struct to mm_struct > From: David Rientjes <rientjes@google.com> > > The per-task oom_adj value is a characteristic of its mm more than the > task itself since it's not possible to oom kill any thread that shares the > mm. If a task were to be killed while attached to an mm that could not be > freed because another thread were set to OOM_DISABLE, it would have > needlessly been terminated since there is no potential for future memory > freeing. > > This patch moves oomkilladj (now more appropriately named oom_adj) from > struct task_struct to struct mm_struct. This requires task_lock() on a > task to check its oom_adj value to protect against exec, but it's already > necessary to take the lock when dereferencing the mm to find the total VM > size for the badness heuristic. > > This fixes a livelock if the oom killer chooses a task and another thread > sharing the same memory has an oom_adj value of OOM_DISABLE. This occurs > because oom_kill_task() repeatedly returns 1 and refuses to kill the > chosen task while select_bad_process() will repeatedly choose the same > task during the next retry. > > Taking task_lock() in select_bad_process() to check for OOM_DISABLE and in > oom_kill_task() to check for threads sharing the same memory will be > removed in the next patch in this series where it will no longer be > necessary. > > Writing to /proc/pid/oom_adj for a kthread will now return -EINVAL since > these threads are immune from oom killing already. They simply report an > oom_adj value of OOM_DISABLE. > > Cc: Nick Piggin <npiggin@suse.de> > Cc: Rik van Riel <riel@redhat.com> > Cc: Mel Gorman <mel@csn.ul.ie> > Signed-off-by: David Rientjes <rientjes@google.com> > Signed-off-by: Andrew Morton <akpm@linux-foundation.org> > --- > > Documentation/filesystems/proc.txt | 15 +++++++---- > fs/proc/base.c | 19 ++++++++++++--- > include/linux/mm_types.h | 2 + > include/linux/sched.h | 1 > mm/oom_kill.c | 34 +++++++++++++++++---------- > 5 files changed, 50 insertions(+), 21 deletions(-) > > diff -puN Documentation/filesystems/proc.txt~oom-move-oom_adj-value-from-task_struct-to-mm_struct Documentation/filesystems/proc.txt > --- a/Documentation/filesystems/proc.txt~oom-move-oom_adj-value-from-task_struct-to-mm_struct > +++ a/Documentation/filesystems/proc.txt > @@ -1003,11 +1003,13 @@ CHAPTER 3: PER-PROCESS PARAMETERS > 3.1 /proc/<pid>/oom_adj - Adjust the oom-killer score > ------------------------------------------------------ > > -This file can be used to adjust the score used to select which processes > -should be killed in an out-of-memory situation. Giving it a high score will > -increase the likelihood of this process being killed by the oom-killer. Valid > -values are in the range -16 to +15, plus the special value -17, which disables > -oom-killing altogether for this process. > +This file can be used to adjust the score used to select which processes should > +be killed in an out-of-memory situation. The oom_adj value is a characteristic > +of the task's mm, so all threads that share an mm with pid will have the same > +oom_adj value. A high value will increase the likelihood of this process being > +killed by the oom-killer. Valid values are in the range -16 to +15 as > +explained below and a special value of -17, which disables oom-killing > +altogether for threads sharing pid's mm. > > The process to be killed in an out-of-memory situation is selected among all others > based on its badness score. This value equals the original memory size of the process > @@ -1021,6 +1023,9 @@ the parent's score if they do not share > are the prime candidates to be killed. Having only one 'hungry' child will make > parent less preferable than the child. > > +/proc/<pid>/oom_adj cannot be changed for kthreads since they are immune from > +oom-killing already. > + > /proc/<pid>/oom_score shows process' current badness score. > > The following heuristics are then applied: > diff -puN fs/proc/base.c~oom-move-oom_adj-value-from-task_struct-to-mm_struct fs/proc/base.c > --- a/fs/proc/base.c~oom-move-oom_adj-value-from-task_struct-to-mm_struct > +++ a/fs/proc/base.c > @@ -1006,7 +1006,12 @@ static ssize_t oom_adjust_read(struct fi > > if (!task) > return -ESRCH; > - oom_adjust = task->oomkilladj; > + task_lock(task); > + if (task->mm) > + oom_adjust = task->mm->oom_adj; > + else > + oom_adjust = OOM_DISABLE; > + task_unlock(task); > put_task_struct(task); > > len = snprintf(buffer, sizeof(buffer), "%i\n", oom_adjust); > @@ -1035,11 +1040,19 @@ static ssize_t oom_adjust_write(struct f > task = get_proc_task(file->f_path.dentry->d_inode); > if (!task) > return -ESRCH; > - if (oom_adjust < task->oomkilladj && !capable(CAP_SYS_RESOURCE)) { > + task_lock(task); > + if (!task->mm) { > + task_unlock(task); > + put_task_struct(task); > + return -EINVAL; > + } > + if (oom_adjust < task->mm->oom_adj && !capable(CAP_SYS_RESOURCE)) { > + task_unlock(task); > put_task_struct(task); > return -EACCES; > } > - task->oomkilladj = oom_adjust; > + task->mm->oom_adj = oom_adjust; > + task_unlock(task); > put_task_struct(task); > if (end - buffer == 0) > return -EIO; > diff -puN include/linux/mm_types.h~oom-move-oom_adj-value-from-task_struct-to-mm_struct include/linux/mm_types.h > --- a/include/linux/mm_types.h~oom-move-oom_adj-value-from-task_struct-to-mm_struct > +++ a/include/linux/mm_types.h > @@ -240,6 +240,8 @@ struct mm_struct { > > unsigned long saved_auxv[AT_VECTOR_SIZE]; /* for /proc/PID/auxv */ > > + s8 oom_adj; /* OOM kill score adjustment (bit shift) */ > + > cpumask_t cpu_vm_mask; > > /* Architecture-specific MM context */ > diff -puN include/linux/sched.h~oom-move-oom_adj-value-from-task_struct-to-mm_struct include/linux/sched.h > --- a/include/linux/sched.h~oom-move-oom_adj-value-from-task_struct-to-mm_struct > +++ a/include/linux/sched.h > @@ -1151,7 +1151,6 @@ struct task_struct { > * a short time > */ > unsigned char fpu_counter; > - s8 oomkilladj; /* OOM kill score adjustment (bit shift). */ > #ifdef CONFIG_BLK_DEV_IO_TRACE > unsigned int btrace_seq; > #endif > diff -puN mm/oom_kill.c~oom-move-oom_adj-value-from-task_struct-to-mm_struct mm/oom_kill.c > --- a/mm/oom_kill.c~oom-move-oom_adj-value-from-task_struct-to-mm_struct > +++ a/mm/oom_kill.c > @@ -58,6 +58,7 @@ unsigned long badness(struct task_struct > unsigned long points, cpu_time, run_time; > struct mm_struct *mm; > struct task_struct *child; > + int oom_adj; > > task_lock(p); > mm = p->mm; > @@ -65,6 +66,7 @@ unsigned long badness(struct task_struct > task_unlock(p); > return 0; > } > + oom_adj = mm->oom_adj; > > /* > * The memory size of the process is the basis for the badness. > @@ -148,15 +150,15 @@ unsigned long badness(struct task_struct > points /= 8; > > /* > - * Adjust the score by oomkilladj. > + * Adjust the score by oom_adj. > */ > - if (p->oomkilladj) { > - if (p->oomkilladj > 0) { > + if (oom_adj) { > + if (oom_adj > 0) { > if (!points) > points = 1; > - points <<= p->oomkilladj; > + points <<= oom_adj; > } else > - points >>= -(p->oomkilladj); > + points >>= -(oom_adj); > } > > #ifdef DEBUG > @@ -251,8 +253,12 @@ static struct task_struct *select_bad_pr > *ppoints = ULONG_MAX; > } > > - if (p->oomkilladj == OOM_DISABLE) > + task_lock(p); > + if (p->mm && p->mm->oom_adj == OOM_DISABLE) { > + task_unlock(p); > continue; > + } > + task_unlock(p); > > points = badness(p, uptime.tv_sec); > if (points > *ppoints || !chosen) { > @@ -304,8 +310,7 @@ static void dump_tasks(const struct mem_ > } > printk(KERN_INFO "[%5d] %5d %5d %8lu %8lu %3d %3d %s\n", > p->pid, __task_cred(p)->uid, p->tgid, mm->total_vm, > - get_mm_rss(mm), (int)task_cpu(p), p->oomkilladj, > - p->comm); > + get_mm_rss(mm), (int)task_cpu(p), mm->oom_adj, p->comm); > task_unlock(p); > } while_each_thread(g, p); > } > @@ -367,8 +372,12 @@ static int oom_kill_task(struct task_str > * Don't kill the process if any threads are set to OOM_DISABLE > */ > do_each_thread(g, q) { > - if (q->mm == mm && q->oomkilladj == OOM_DISABLE) > + task_lock(q); > + if (q->mm == mm && q->mm && q->mm->oom_adj == OOM_DISABLE) { > + task_unlock(q); > return 1; > + } > + task_unlock(q); > } while_each_thread(g, q); > > __oom_kill_task(p, 1); > @@ -393,10 +402,11 @@ static int oom_kill_process(struct task_ > struct task_struct *c; > > if (printk_ratelimit()) { > - printk(KERN_WARNING "%s invoked oom-killer: " > - "gfp_mask=0x%x, order=%d, oomkilladj=%d\n", > - current->comm, gfp_mask, order, current->oomkilladj); > task_lock(current); > + printk(KERN_WARNING "%s invoked oom-killer: " > + "gfp_mask=0x%x, order=%d, oom_adj=%d\n", > + current->comm, gfp_mask, order, > + current->mm ? current->mm->oom_adj : OOM_DISABLE); > cpuset_print_task_mems_allowed(current); > task_unlock(current); > dump_stack(); > _ > > Patches currently in -mm which might be from rientjes@google.com are > > origin.patch > linux-next.patch > cpusets-restructure-the-function-cpuset_update_task_memory_state.patch > cpusets-update-tasks-page-slab-spread-flags-in-time.patch > cpusetmm-update-tasks-mems_allowed-in-time.patch > cpusetmm-update-tasks-mems_allowed-in-time-fix.patch > cpusetmm-update-tasks-mems_allowed-in-time-cleanup.patch > page-allocator-use-a-pre-calculated-value-instead-of-num_online_nodes-in-fast-paths-do-not-override-definition-of-node_set_online-with-macro.patch > mm-setup_per_zone_inactive_ratio-do-not-call-for-int_sqrt-if-not-needed.patch > mm-setup_per_zone_inactive_ratio-fix-comment-and-make-it-__init.patch > page-allocator-warn-if-__gfp_nofail-is-used-for-a-large-allocation.patch > mm-pm-freezer-disable-oom-killer-when-tasks-are-frozen.patch > oom-move-oom_adj-value-from-task_struct-to-mm_struct.patch > oom-avoid-unnecessary-mm-locking-and-scanning-for-oom_disable.patch > memcg-add-file-based-rss-accounting.patch > memcg-add-file-based-rss-accounting-fix-mem_cgroup_update_mapped_file_stat-oops.patch > > -- > To unsubscribe from this list: send the line "unsubscribe mm-commits" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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