Re: [PATCH v1] mm: Add configuration to control whether vmpressure notifier is enabled

[yong w <yongw.pur@gmail.com>]

Hu Haowen <src.res@email.cn> 于2021年8月13日周五 下午9:45写道：
>
>
> 在 2021/8/13 下午7:57, yongw.pur@gmail.com 写道:
> > From: wangyong <wang.yong12@zte.com.cn>
> >
> > Inspired by PSI features, vmpressure inotifier function should also be
> > configured to decide whether it is used, because it is an independent
> > feature which notifies the user of memory pressure.
> >
> > Since the vmpressure interface is used in kernel common code, for
> > users who do not use the vmpressure function, there will be
> > additional overhead.
> >
> > So we add configuration to control whether vmpressure notifier is
> > enabled, and provide a boot parameter to use use vmpressure notifier
> > flexibly
> >
> > Signed-off-by: wangyong <wang.yong12@zte.com.cn>
> > ---
> >  Documentation/admin-guide/cgroup-v1/memory.rst  |  3 ++-
> >  Documentation/admin-guide/kernel-parameters.txt |  3 +++
> >  include/linux/memcontrol.h                      |  2 ++
> >  include/linux/vmpressure.h                      |  7 +++++--
> >  init/Kconfig                                    | 20 +++++++++++++++++++
> >  mm/Makefile                                     |  3 ++-
> >  mm/memcontrol.c                                 |  7 ++++++-
> >  mm/vmpressure.c                                 | 26 +++++++++++++++++++++++++
> >  8 files changed, 66 insertions(+), 5 deletions(-)
> >
> > diff --git a/Documentation/admin-guide/cgroup-v1/memory.rst b/Documentation/admin-guide/cgroup-v1/memory.rst
> > index 41191b5..967418a 100644
> > --- a/Documentation/admin-guide/cgroup-v1/memory.rst
> > +++ b/Documentation/admin-guide/cgroup-v1/memory.rst
> > @@ -388,6 +388,7 @@ a. Enable CONFIG_CGROUPS
> >  b. Enable CONFIG_MEMCG
> >  c. Enable CONFIG_MEMCG_SWAP (to use swap extension)
> >  d. Enable CONFIG_MEMCG_KMEM (to use kmem extension)
> > +e. Enable CONFIG_MEMCG_VMPRESSURE (to use vmpressure extension)
> >
> >  3.1. Prepare the cgroups (see cgroups.txt, Why are cgroups needed?)
> >  -------------------------------------------------------------------
> > @@ -855,7 +856,7 @@ At reading, current status of OOM is shown.
> >            The number of processes belonging to this cgroup killed by any
> >            kind of OOM killer.
> >
> > -11. Memory Pressure
> > +11. Memory Pressure (CONFIG_MEMCG_VMPRESSURE)
> >  ===================
> >
>
>
> Please replace:
>
> 11. Memory Pressure (CONFIG_MEMCG_VMPRESSURE)
> ===================
>
> with:
>
> 11. Memory Pressure (CONFIG_MEMCG_VMPRESSURE)
> =============================================
>
> Cheers,
> Hu Haowen
>
Thank you for your reply, I will modify it in the next patch.
Are there any other questions about this patch?

Thanks.
> >  The pressure level notifications can be used to monitor the memory
> > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> > index 4042a82..d119fb8 100644
> > --- a/Documentation/admin-guide/kernel-parameters.txt
> > +++ b/Documentation/admin-guide/kernel-parameters.txt
> > @@ -6158,6 +6158,9 @@
> >       vmpoff=         [KNL,S390] Perform z/VM CP command after power off.
> >                       Format: <command>
> >
> > +     vmpressure=     [KNL] Enable or disable vmpressure notifier.
> > +                     Format: <bool>
> > +
> >       vsyscall=       [X86-64]
> >                       Controls the behavior of vsyscalls (i.e. calls to
> >                       fixed addresses of 0xffffffffff600x00 from legacy
> > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> > index 0ff1464..b201d8e 100644
> > --- a/include/linux/memcontrol.h
> > +++ b/include/linux/memcontrol.h
> > @@ -257,8 +257,10 @@ struct mem_cgroup {
> >
> >       unsigned long soft_limit;
> >
> > +#ifdef CONFIG_MEMCG_VMPRESSURE
> >       /* vmpressure notifications */
> >       struct vmpressure vmpressure;
> > +#endif
> >
> >       /*
> >        * Should the OOM killer kill all belonging tasks, had it kill one?
> > diff --git a/include/linux/vmpressure.h b/include/linux/vmpressure.h
> > index 6a2f51e..dcae02e 100644
> > --- a/include/linux/vmpressure.h
> > +++ b/include/linux/vmpressure.h
> > @@ -29,7 +29,8 @@ struct vmpressure {
> >
> >  struct mem_cgroup;
> >
> > -#ifdef CONFIG_MEMCG
> > +#ifdef CONFIG_MEMCG_VMPRESSURE
> > +extern bool vmpressure_enable;
> >  extern void vmpressure(gfp_t gfp, struct mem_cgroup *memcg, bool tree,
> >                      unsigned long scanned, unsigned long reclaimed);
> >  extern void vmpressure_prio(gfp_t gfp, struct mem_cgroup *memcg, int prio);
> > @@ -48,5 +49,7 @@ static inline void vmpressure(gfp_t gfp, struct mem_cgroup *memcg, bool tree,
> >                             unsigned long scanned, unsigned long reclaimed) {}
> >  static inline void vmpressure_prio(gfp_t gfp, struct mem_cgroup *memcg,
> >                                  int prio) {}
> > -#endif /* CONFIG_MEMCG */
> > +static inline void vmpressure_init(struct vmpressure *vmpr) {}
> > +static inline void vmpressure_cleanup(struct vmpressure *vmpr) {}
> > +#endif /* CONFIG_MEMCG_PRESSURE */
> >  #endif /* __LINUX_VMPRESSURE_H */
> > diff --git a/init/Kconfig b/init/Kconfig
> > index 71a028d..d3afeb2 100644
> > --- a/init/Kconfig
> > +++ b/init/Kconfig
> > @@ -948,6 +948,26 @@ config MEMCG_KMEM
> >       depends on MEMCG && !SLOB
> >       default y
> >
> > +config MEMCG_VMPRESSURE
> > +     bool "Memory pressure notifier"
> > +     depends on MEMCG
> > +     default y
> > +     help
> > +       Vmpressure extension is used to monitor the memory allocation cost.
> > +       The pressure level can be set according to the use scenario and
> > +       application will be notified through eventfd when memory pressure is at
> > +       the specific level (or higher).
> > +
> > +config VMPRESSURE_DEFAULT_DISABLED
> > +     bool "Require boot parameter to enable memory pressure notifier"
> > +     depends on MEMCG_VMPRESSURE
> > +     default n
> > +     help
> > +       If set, memory pressure notifier will be disabled  but can be
> > +       enabled through passing vmpressure=1 on the kernel commandline
> > +       during boot.
> > +       For those who want to use memory pressure notifier flexibly.
> > +
> >  config BLK_CGROUP
> >       bool "IO controller"
> >       depends on BLOCK
> > diff --git a/mm/Makefile b/mm/Makefile
> > index 970604e..e4f99c1 100644
> > --- a/mm/Makefile
> > +++ b/mm/Makefile
> > @@ -92,7 +92,8 @@ obj-$(CONFIG_MEMTEST)               += memtest.o
> >  obj-$(CONFIG_MIGRATION) += migrate.o
> >  obj-$(CONFIG_TRANSPARENT_HUGEPAGE) += huge_memory.o khugepaged.o
> >  obj-$(CONFIG_PAGE_COUNTER) += page_counter.o
> > -obj-$(CONFIG_MEMCG) += memcontrol.o vmpressure.o
> > +obj-$(CONFIG_MEMCG) += memcontrol.o
> > +obj-$(CONFIG_MEMCG_VMPRESSURE) += vmpressure.o
> >  obj-$(CONFIG_MEMCG_SWAP) += swap_cgroup.o
> >  obj-$(CONFIG_CGROUP_HUGETLB) += hugetlb_cgroup.o
> >  obj-$(CONFIG_GUP_TEST) += gup_test.o
> > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> > index 3e7c205..ee060ae2 100644
> > --- a/mm/memcontrol.c
> > +++ b/mm/memcontrol.c
> > @@ -248,6 +248,7 @@ static inline bool should_force_charge(void)
> >               (current->flags & PF_EXITING);
> >  }
> >
> > +#ifdef CONFIG_MEMCG_VMPRESSURE
> >  /* Some nice accessors for the vmpressure. */
> >  struct vmpressure *memcg_to_vmpressure(struct mem_cgroup *memcg)
> >  {
> > @@ -260,6 +261,7 @@ struct mem_cgroup *vmpressure_to_memcg(struct vmpressure *vmpr)
> >  {
> >       return container_of(vmpr, struct mem_cgroup, vmpressure);
> >  }
> > +#endif
> >
> >  #ifdef CONFIG_MEMCG_KMEM
> >  extern spinlock_t css_set_lock;
> > @@ -4794,9 +4796,12 @@ static ssize_t memcg_write_event_control(struct kernfs_open_file *of,
> >       } else if (!strcmp(name, "memory.oom_control")) {
> >               event->register_event = mem_cgroup_oom_register_event;
> >               event->unregister_event = mem_cgroup_oom_unregister_event;
> > -     } else if (!strcmp(name, "memory.pressure_level")) {
> > +#ifdef CONFIG_MEMCG_VMPRESSURE
> > +     } else if (vmpressure_enable &&
> > +                !strcmp(name, "memory.pressure_level")) {
> >               event->register_event = vmpressure_register_event;
> >               event->unregister_event = vmpressure_unregister_event;
> > +#endif
> >       } else if (!strcmp(name, "memory.memsw.usage_in_bytes")) {
> >               event->register_event = memsw_cgroup_usage_register_event;
> >               event->unregister_event = memsw_cgroup_usage_unregister_event;
> > diff --git a/mm/vmpressure.c b/mm/vmpressure.c
> > index 76518e4..b0d4358 100644
> > --- a/mm/vmpressure.c
> > +++ b/mm/vmpressure.c
> > @@ -67,6 +67,19 @@ static const unsigned int vmpressure_level_critical = 95;
> >   */
> >  static const unsigned int vmpressure_level_critical_prio = ilog2(100 / 10);
> >
> > +DEFINE_STATIC_KEY_FALSE(vmpressure_disabled);
> > +#ifdef CONFIG_VMPRESSURE_DEFAULT_DISABLED
> > +bool vmpressure_enable;
> > +#else
> > +bool vmpressure_enable = true;
> > +#endif
> > +static int __init setup_vmpressure(char *str)
> > +{
> > +     return kstrtobool(str, &vmpressure_enable) == 0;
> > +}
> > +__setup("vmpressure=", setup_vmpressure);
> > +
> > +
> >  static struct vmpressure *work_to_vmpressure(struct work_struct *work)
> >  {
> >       return container_of(work, struct vmpressure, work);
> > @@ -246,6 +259,9 @@ void vmpressure(gfp_t gfp, struct mem_cgroup *memcg, bool tree,
> >
> >       vmpr = memcg_to_vmpressure(memcg);
> >
> > +     if (static_branch_likely(&vmpressure_disabled))
> > +             return;
> > +
> >       /*
> >        * Here we only want to account pressure that userland is able to
> >        * help us with. For example, suppose that DMA zone is under
> > @@ -326,6 +342,8 @@ void vmpressure(gfp_t gfp, struct mem_cgroup *memcg, bool tree,
> >   */
> >  void vmpressure_prio(gfp_t gfp, struct mem_cgroup *memcg, int prio)
> >  {
> > +     if (static_branch_likely(&vmpressure_disabled))
> > +             return;
> >       /*
> >        * We only use prio for accounting critical level. For more info
> >        * see comment for vmpressure_level_critical_prio variable above.
> > @@ -450,6 +468,11 @@ void vmpressure_unregister_event(struct mem_cgroup *memcg,
> >   */
> >  void vmpressure_init(struct vmpressure *vmpr)
> >  {
> > +     if (!vmpressure_enable) {
> > +             static_branch_enable(&vmpressure_disabled);
> > +             return;
> > +     }
> > +
> >       spin_lock_init(&vmpr->sr_lock);
> >       mutex_init(&vmpr->events_lock);
> >       INIT_LIST_HEAD(&vmpr->events);
> > @@ -465,6 +488,9 @@ void vmpressure_init(struct vmpressure *vmpr)
> >   */
> >  void vmpressure_cleanup(struct vmpressure *vmpr)
> >  {
> > +
> > +     if (static_branch_likely(&vmpressure_disabled))
> > +             return;
> >       /*
> >        * Make sure there is no pending work before eventfd infrastructure
> >        * goes away.
>