Re: [PATCH] Make SPLIT_RSS_COUNTING configurable

[Daniel Colascione]

Adding the correct linux-mm address.


On Wed, Oct 2, 2019 at 1:25 PM Daniel Colascione <dancol@xxxxxxxxxx> wrote:
>
> Using the new config option, users can disable SPLIT_RSS_COUNTING to
> get increased accuracy in user-visible mm counters.
>
> Signed-off-by: Daniel Colascione <dancol@xxxxxxxxxx>
> ---
>  include/linux/mm.h            |  4 ++--
>  include/linux/mm_types_task.h |  5 ++---
>  include/linux/sched.h         |  2 +-
>  kernel/fork.c                 |  2 +-
>  mm/Kconfig                    | 11 +++++++++++
>  mm/memory.c                   |  6 +++---
>  6 files changed, 20 insertions(+), 10 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index cc292273e6ba..221395de3cb4 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1637,7 +1637,7 @@ static inline unsigned long get_mm_counter(struct mm_struct *mm, int member)
>  {
>         long val = atomic_long_read(&mm->rss_stat.count[member]);
>
> -#ifdef SPLIT_RSS_COUNTING
> +#ifdef CONFIG_SPLIT_RSS_COUNTING
>         /*
>          * counter is updated in asynchronous manner and may go to minus.
>          * But it's never be expected number for users.
> @@ -1723,7 +1723,7 @@ static inline void setmax_mm_hiwater_rss(unsigned long *maxrss,
>                 *maxrss = hiwater_rss;
>  }
>
> -#if defined(SPLIT_RSS_COUNTING)
> +#ifdef CONFIG_SPLIT_RSS_COUNTING
>  void sync_mm_rss(struct mm_struct *mm);
>  #else
>  static inline void sync_mm_rss(struct mm_struct *mm)
> diff --git a/include/linux/mm_types_task.h b/include/linux/mm_types_task.h
> index c1bc6731125c..d2adc8057e65 100644
> --- a/include/linux/mm_types_task.h
> +++ b/include/linux/mm_types_task.h
> @@ -48,14 +48,13 @@ enum {
>         NR_MM_COUNTERS
>  };
>
> -#if USE_SPLIT_PTE_PTLOCKS && defined(CONFIG_MMU)
> -#define SPLIT_RSS_COUNTING
> +#ifdef CONFIG_SPLIT_RSS_COUNTING
>  /* per-thread cached information, */
>  struct task_rss_stat {
>         int events;     /* for synchronization threshold */
>         int count[NR_MM_COUNTERS];
>  };
> -#endif /* USE_SPLIT_PTE_PTLOCKS */
> +#endif /* CONFIG_SPLIT_RSS_COUNTING */
>
>  struct mm_rss_stat {
>         atomic_long_t count[NR_MM_COUNTERS];
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index 2c2e56bd8913..22f354774540 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -729,7 +729,7 @@ struct task_struct {
>         /* Per-thread vma caching: */
>         struct vmacache                 vmacache;
>
> -#ifdef SPLIT_RSS_COUNTING
> +#ifdef CONFIG_SPLIT_RSS_COUNTING
>         struct task_rss_stat            rss_stat;
>  #endif
>         int                             exit_state;
> diff --git a/kernel/fork.c b/kernel/fork.c
> index f9572f416126..fc5e0889922b 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -1917,7 +1917,7 @@ static __latent_entropy struct task_struct *copy_process(
>         p->vtime.state = VTIME_INACTIVE;
>  #endif
>
> -#if defined(SPLIT_RSS_COUNTING)
> +#ifdef CONFIG_SPLIT_RSS_COUNTING
>         memset(&p->rss_stat, 0, sizeof(p->rss_stat));
>  #endif
>
> diff --git a/mm/Kconfig b/mm/Kconfig
> index a5dae9a7eb51..372ef9449924 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -736,4 +736,15 @@ config ARCH_HAS_PTE_SPECIAL
>  config ARCH_HAS_HUGEPD
>         bool
>
> +config SPLIT_RSS_COUNTING
> +       bool "Per-thread mm counter caching"
> +       depends on MMU
> +       default y if NR_CPUS >= SPLIT_PTLOCK_CPUS
> +       help
> +         Cache mm counter updates in thread structures and
> +         flush them to visible per-process statistics in batches.
> +         Say Y here to slightly reduce cache contention in processes
> +         with many threads at the expense of decreasing the accuracy
> +         of memory statistics in /proc.
> +
>  endmenu
> diff --git a/mm/memory.c b/mm/memory.c
> index b1ca51a079f2..bf557ed5ba23 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -141,7 +141,7 @@ static int __init init_zero_pfn(void)
>  core_initcall(init_zero_pfn);
>
>
> -#if defined(SPLIT_RSS_COUNTING)
> +#ifdef CONFIG_SPLIT_RSS_COUNTING
>
>  void sync_mm_rss(struct mm_struct *mm)
>  {
> @@ -177,7 +177,7 @@ static void check_sync_rss_stat(struct task_struct *task)
>         if (unlikely(task->rss_stat.events++ > TASK_RSS_EVENTS_THRESH))
>                 sync_mm_rss(task->mm);
>  }
> -#else /* SPLIT_RSS_COUNTING */
> +#else /* CONFIG_SPLIT_RSS_COUNTING */
>
>  #define inc_mm_counter_fast(mm, member) inc_mm_counter(mm, member)
>  #define dec_mm_counter_fast(mm, member) dec_mm_counter(mm, member)
> @@ -186,7 +186,7 @@ static void check_sync_rss_stat(struct task_struct *task)
>  {
>  }
>
> -#endif /* SPLIT_RSS_COUNTING */
> +#endif /* CONFIG_SPLIT_RSS_COUNTING */
>
>  /*
>   * Note: this doesn't free the actual pages themselves. That
> --
> 2.23.0.581.g78d2f28ef7-goog
>