Re: [PATCH] Make SPLIT_RSS_COUNTING configurable

Daniel Colascione
2019-10-02T20:29:27Z

Adding the correct linux-mm address.

On Wed, Oct 2, 2019 at 1:25 PM Daniel Colascione <dancol@google.com> 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@google.com>
> ---
> 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
>