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    SubjectRe: [patch 5/7 -mm] oom: replace sysctls with quick mode
    On Wed, 10 Feb 2010 08:32:17 -0800 (PST)
    David Rientjes <rientjes@google.com> wrote:

    > Two VM sysctls, oom dump_tasks and oom_kill_allocating_task, were
    > implemented for very large systems to avoid excessively long tasklist
    > scans. The former suppresses helpful diagnostic messages that are
    > emitted for each thread group leader that are candidates for oom kill
    > including their pid, uid, vm size, rss, oom_adj value, and name; this
    > information is very helpful to users in understanding why a particular
    > task was chosen for kill over others. The latter simply kills current,
    > the task triggering the oom condition, instead of iterating through the
    > tasklist looking for the worst offender.
    >
    > Both of these sysctls are combined into one for use on the aforementioned
    > large systems: oom_kill_quick. This disables the now-default
    > oom_dump_tasks and kills current whenever the oom killer is called.
    >
    > The oom killer rewrite is the perfect opportunity to combine both sysctls
    > into one instead of carrying around the others for years to come for
    > nothing else than legacy purposes.
    >
    > Signed-off-by: David Rientjes <rientjes@google.com>

    seems reasonable..but how old these APIs are ? Replacement is ok ?

    Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>


    > ---
    > Documentation/sysctl/vm.txt | 44 +++++-------------------------------------
    > include/linux/oom.h | 3 +-
    > kernel/sysctl.c | 13 ++---------
    > mm/oom_kill.c | 9 +++----
    > 4 files changed, 14 insertions(+), 55 deletions(-)
    >
    > diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt
    > --- a/Documentation/sysctl/vm.txt
    > +++ b/Documentation/sysctl/vm.txt
    > @@ -43,9 +43,8 @@ Currently, these files are in /proc/sys/vm:
    > - nr_pdflush_threads
    > - nr_trim_pages (only if CONFIG_MMU=n)
    > - numa_zonelist_order
    > -- oom_dump_tasks
    > - oom_forkbomb_thres
    > -- oom_kill_allocating_task
    > +- oom_kill_quick
    > - overcommit_memory
    > - overcommit_ratio
    > - page-cluster
    > @@ -470,27 +469,6 @@ this is causing problems for your system/application.
    >
    > ==============================================================
    >
    > -oom_dump_tasks
    > -
    > -Enables a system-wide task dump (excluding kernel threads) to be
    > -produced when the kernel performs an OOM-killing and includes such
    > -information as pid, uid, tgid, vm size, rss, cpu, oom_adj score, and
    > -name. This is helpful to determine why the OOM killer was invoked
    > -and to identify the rogue task that caused it.
    > -
    > -If this is set to zero, this information is suppressed. On very
    > -large systems with thousands of tasks it may not be feasible to dump
    > -the memory state information for each one. Such systems should not
    > -be forced to incur a performance penalty in OOM conditions when the
    > -information may not be desired.
    > -
    > -If this is set to non-zero, this information is shown whenever the
    > -OOM killer actually kills a memory-hogging task.
    > -
    > -The default value is 0.
    > -
    > -==============================================================
    > -
    > oom_forkbomb_thres
    >
    > This value defines how many children with a seperate address space a specific
    > @@ -511,22 +489,12 @@ The default value is 1000.
    >
    > ==============================================================
    >
    > -oom_kill_allocating_task
    > -
    > -This enables or disables killing the OOM-triggering task in
    > -out-of-memory situations.
    > -
    > -If this is set to zero, the OOM killer will scan through the entire
    > -tasklist and select a task based on heuristics to kill. This normally
    > -selects a rogue memory-hogging task that frees up a large amount of
    > -memory when killed.
    > -
    > -If this is set to non-zero, the OOM killer simply kills the task that
    > -triggered the out-of-memory condition. This avoids the expensive
    > -tasklist scan.
    > +oom_kill_quick
    >
    > -If panic_on_oom is selected, it takes precedence over whatever value
    > -is used in oom_kill_allocating_task.
    > +When enabled, this will always kill the task that triggered the oom killer, i.e.
    > +the task that attempted to allocate memory that could not be found. It also
    > +suppresses the tasklist dump to the kernel log whenever the oom killer is
    > +called. Typically set on systems with an extremely large number of tasks.
    >
    > The default value is 0.
    >
    > diff --git a/include/linux/oom.h b/include/linux/oom.h
    > --- a/include/linux/oom.h
    > +++ b/include/linux/oom.h
    > @@ -51,8 +51,7 @@ static inline void oom_killer_enable(void)
    > }
    > /* for sysctl */
    > extern int sysctl_panic_on_oom;
    > -extern int sysctl_oom_kill_allocating_task;
    > -extern int sysctl_oom_dump_tasks;
    > +extern int sysctl_oom_kill_quick;
    > extern int sysctl_oom_forkbomb_thres;
    >
    > #endif /* __KERNEL__*/
    > diff --git a/kernel/sysctl.c b/kernel/sysctl.c
    > --- a/kernel/sysctl.c
    > +++ b/kernel/sysctl.c
    > @@ -949,16 +949,9 @@ static struct ctl_table vm_table[] = {
    > .proc_handler = proc_dointvec,
    > },
    > {
    > - .procname = "oom_kill_allocating_task",
    > - .data = &sysctl_oom_kill_allocating_task,
    > - .maxlen = sizeof(sysctl_oom_kill_allocating_task),
    > - .mode = 0644,
    > - .proc_handler = proc_dointvec,
    > - },
    > - {
    > - .procname = "oom_dump_tasks",
    > - .data = &sysctl_oom_dump_tasks,
    > - .maxlen = sizeof(sysctl_oom_dump_tasks),
    > + .procname = "oom_kill_quick",
    > + .data = &sysctl_oom_kill_quick,
    > + .maxlen = sizeof(sysctl_oom_kill_quick),
    > .mode = 0644,
    > .proc_handler = proc_dointvec,
    > },
    > diff --git a/mm/oom_kill.c b/mm/oom_kill.c
    > --- a/mm/oom_kill.c
    > +++ b/mm/oom_kill.c
    > @@ -32,9 +32,8 @@
    > #include <linux/security.h>
    >
    > int sysctl_panic_on_oom;
    > -int sysctl_oom_kill_allocating_task;
    > -int sysctl_oom_dump_tasks;
    > int sysctl_oom_forkbomb_thres = DEFAULT_OOM_FORKBOMB_THRES;
    > +int sysctl_oom_kill_quick;
    > static DEFINE_SPINLOCK(zone_scan_lock);
    >
    > /*
    > @@ -397,7 +396,7 @@ static void dump_header(struct task_struct *p, gfp_t gfp_mask, int order,
    > dump_stack();
    > mem_cgroup_print_oom_info(mem, p);
    > show_mem();
    > - if (sysctl_oom_dump_tasks)
    > + if (!sysctl_oom_kill_quick)
    > dump_tasks(mem);
    > }
    >
    > @@ -604,9 +603,9 @@ static void __out_of_memory(gfp_t gfp_mask, int order, unsigned long totalpages,
    > struct task_struct *p;
    > unsigned int points;
    >
    > - if (sysctl_oom_kill_allocating_task)
    > + if (sysctl_oom_kill_quick)
    > if (!oom_kill_process(current, gfp_mask, order, 0, totalpages,
    > - NULL, "Out of memory (oom_kill_allocating_task)"))
    > + NULL, "Out of memory (quick mode)"))
    > return;
    > retry:
    > /*
    >
    > --
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