Re: [PATCH 1/3 staging-next] android: Collect statistics from lowmemorykiller

[Michal Hocko]

On Thu 09-02-17 14:21:45, peter enderborg wrote:
> This collects stats for shrinker calls and how much
> waste work we do within the lowmemorykiller.

This doesn't explain why do we need this information and who is going to
use it. Not to mention it exports it in /proc which is considered a
stable user API. This is a no-go, especially for something that is still
lingering in the staging tree without any actuall effort to make it
fully supported MM feature. I am actually strongly inclined to simply
drop lmk from the tree completely.

> Signed-off-by: Peter Enderborg <peter.enderborg@xxxxxxxxxxxxxx>

Nacked-by: Michal Hocko <mhocko@xxxxxxxx>

> ---
>  drivers/staging/android/Kconfig                 | 11 ++++
>  drivers/staging/android/Makefile                |  1 +
>  drivers/staging/android/lowmemorykiller.c       |  9 ++-
>  drivers/staging/android/lowmemorykiller_stats.c | 85 +++++++++++++++++++++++++
>  drivers/staging/android/lowmemorykiller_stats.h | 29 +++++++++
>  5 files changed, 134 insertions(+), 1 deletion(-)
>  create mode 100644 drivers/staging/android/lowmemorykiller_stats.c
>  create mode 100644 drivers/staging/android/lowmemorykiller_stats.h
> 
> diff --git a/drivers/staging/android/Kconfig b/drivers/staging/android/Kconfig
> index 6c00d6f..96e86c7 100644
> --- a/drivers/staging/android/Kconfig
> +++ b/drivers/staging/android/Kconfig
> @@ -24,6 +24,17 @@ config ANDROID_LOW_MEMORY_KILLER
>        scripts (/init.rc), and it defines priority values with minimum free memory size
>        for each priority.
> 
> +config ANDROID_LOW_MEMORY_KILLER_STATS
> +    bool "Android Low Memory Killer: collect statistics"
> +    depends on ANDROID_LOW_MEMORY_KILLER
> +    default n
> +    help
> +      Create a file in /proc/lmkstats that includes
> +      collected statistics about kills, scans and counts
> +      and  interaction with the shrinker. Its content
> +      will be different depeding on lmk implementation used.
> +
> +
>  source "drivers/staging/android/ion/Kconfig"
> 
>  endif # if ANDROID
> diff --git a/drivers/staging/android/Makefile b/drivers/staging/android/Makefile
> index 7ed1be7..d710eb2 100644
> --- a/drivers/staging/android/Makefile
> +++ b/drivers/staging/android/Makefile
> @@ -4,3 +4,4 @@ obj-y                    += ion/
> 
>  obj-$(CONFIG_ASHMEM)            += ashmem.o
>  obj-$(CONFIG_ANDROID_LOW_MEMORY_KILLER)    += lowmemorykiller.o
> +obj-$(CONFIG_ANDROID_LOW_MEMORY_KILLER_STATS)    += lowmemorykiller_stats.o
> diff --git a/drivers/staging/android/lowmemorykiller.c b/drivers/staging/android/lowmemorykiller.c
> index ec3b665..15c1b38 100644
> --- a/drivers/staging/android/lowmemorykiller.c
> +++ b/drivers/staging/android/lowmemorykiller.c
> @@ -42,6 +42,7 @@
>  #include <linux/rcupdate.h>
>  #include <linux/profile.h>
>  #include <linux/notifier.h>
> +#include "lowmemorykiller_stats.h"
> 
>  static u32 lowmem_debug_level = 1;
>  static short lowmem_adj[6] = {
> @@ -72,6 +73,7 @@ static unsigned long lowmem_deathpending_timeout;
>  static unsigned long lowmem_count(struct shrinker *s,
>                    struct shrink_control *sc)
>  {
> +    lmk_inc_stats(LMK_COUNT);
>      return global_node_page_state(NR_ACTIVE_ANON) +
>          global_node_page_state(NR_ACTIVE_FILE) +
>          global_node_page_state(NR_INACTIVE_ANON) +
> @@ -95,6 +97,7 @@ static unsigned long lowmem_scan(struct shrinker *s, struct shrink_control *sc)
>                  global_node_page_state(NR_SHMEM) -
>                  total_swapcache_pages();
> 
> +    lmk_inc_stats(LMK_SCAN);
>      if (lowmem_adj_size < array_size)
>          array_size = lowmem_adj_size;
>      if (lowmem_minfree_size < array_size)
> @@ -134,6 +137,7 @@ static unsigned long lowmem_scan(struct shrinker *s, struct shrink_control *sc)
>          if (task_lmk_waiting(p) &&
>              time_before_eq(jiffies, lowmem_deathpending_timeout)) {
>              task_unlock(p);
> +            lmk_inc_stats(LMK_TIMEOUT);
>              rcu_read_unlock();
>              return 0;
>          }
> @@ -179,7 +183,9 @@ static unsigned long lowmem_scan(struct shrinker *s, struct shrink_control *sc)
>                   other_free * (long)(PAGE_SIZE / 1024));
>          lowmem_deathpending_timeout = jiffies + HZ;
>          rem += selected_tasksize;
> -    }
> +        lmk_inc_stats(LMK_KILL);
> +    } else
> +        lmk_inc_stats(LMK_WASTE);
> 
>      lowmem_print(4, "lowmem_scan %lu, %x, return %lu\n",
>               sc->nr_to_scan, sc->gfp_mask, rem);
> @@ -196,6 +202,7 @@ static struct shrinker lowmem_shrinker = {
>  static int __init lowmem_init(void)
>  {
>      register_shrinker(&lowmem_shrinker);
> +    init_procfs_lmk();
>      return 0;
>  }
>  device_initcall(lowmem_init);
> diff --git a/drivers/staging/android/lowmemorykiller_stats.c b/drivers/staging/android/lowmemorykiller_stats.c
> new file mode 100644
> index 0000000..673691c
> --- /dev/null
> +++ b/drivers/staging/android/lowmemorykiller_stats.c
> @@ -0,0 +1,85 @@
> +/*
> + *  lowmemorykiller_stats
> + *
> + *  Copyright (C) 2017 Sony Mobile Communications Inc.
> + *
> + *  Author: Peter Enderborg <peter.enderborg@xxxxxxxxxxxxxx>
> + *
> + *  This program is free software; you can redistribute it and/or modify
> + *  it under the terms of the GNU General Public License version 2 as
> + *  published by the Free Software Foundation.
> + */
> +/* This code is bookkeeping of statistical information
> + * from lowmemorykiller and provide a node in proc "/proc/lmkstats".
> + */
> +
> +#include <linux/proc_fs.h>
> +#include <linux/seq_file.h>
> +#include "lowmemorykiller_stats.h"
> +
> +struct lmk_stats {
> +    atomic_long_t scans; /* counter as in shrinker scans */
> +    atomic_long_t kills; /* the number of sigkills sent */
> +    atomic_long_t waste; /* the numer of extensive calls that did
> +                  * not lead to anything
> +                  */
> +    atomic_long_t timeout; /* counter for shrinker calls that needed
> +                * to be cancelled due to pending kills
> +                */
> +    atomic_long_t count; /* number of shrinker count calls */
> +    atomic_long_t unknown; /* internal */
> +} st;
> +
> +void lmk_inc_stats(int key)
> +{
> +    switch (key) {
> +    case LMK_SCAN:
> +        atomic_long_inc(&st.scans);
> +        break;
> +    case LMK_KILL:
> +        atomic_long_inc(&st.kills);
> +        break;
> +    case LMK_WASTE:
> +        atomic_long_inc(&st.waste);
> +        break;
> +    case LMK_TIMEOUT:
> +        atomic_long_inc(&st.timeout);
> +        break;
> +    case LMK_COUNT:
> +        atomic_long_inc(&st.count);
> +        break;
> +    default:
> +        atomic_long_inc(&st.unknown);
> +        break;
> +    }
> +}
> +
> +static int lmk_proc_show(struct seq_file *m, void *v)
> +{
> +    seq_printf(m, "kill: %ld\n", atomic_long_read(&st.kills));
> +    seq_printf(m, "scan: %ld\n", atomic_long_read(&st.scans));
> +    seq_printf(m, "waste: %ld\n", atomic_long_read(&st.waste));
> +    seq_printf(m, "timeout: %ld\n", atomic_long_read(&st.timeout));
> +    seq_printf(m, "count: %ld\n", atomic_long_read(&st.count));
> +    seq_printf(m, "unknown: %ld (internal)\n",
> +           atomic_long_read(&st.unknown));
> +
> +    return 0;
> +}
> +
> +static int lmk_proc_open(struct inode *inode, struct file *file)
> +{
> +    return single_open(file, lmk_proc_show, PDE_DATA(inode));
> +}
> +
> +static const struct file_operations lmk_proc_fops = {
> +    .open        = lmk_proc_open,
> +    .read        = seq_read,
> +    .release    = single_release
> +};
> +
> +int __init init_procfs_lmk(void)
> +{
> +    proc_create_data(LMK_PROCFS_NAME, 0444, NULL, &lmk_proc_fops, NULL);
> +    return 0;
> +}
> diff --git a/drivers/staging/android/lowmemorykiller_stats.h b/drivers/staging/android/lowmemorykiller_stats.h
> new file mode 100644
> index 0000000..abeb6924
> --- /dev/null
> +++ b/drivers/staging/android/lowmemorykiller_stats.h
> @@ -0,0 +1,29 @@
> +/*
> + *  lowmemorykiller_stats interface
> + *
> + *  Copyright (C) 2017 Sony Mobile Communications Inc.
> + *
> + *  Author: Peter Enderborg <peter.enderborg@xxxxxxxxxxxxxx>
> + *
> + *  This program is free software; you can redistribute it and/or modify
> + *  it under the terms of the GNU General Public License version 2 as
> + *  published by the Free Software Foundation.
> + */
> +
> +enum  lmk_kill_stats {
> +    LMK_SCAN = 1,
> +    LMK_KILL = 2,
> +    LMK_WASTE = 3,
> +    LMK_TIMEOUT = 4,
> +    LMK_COUNT = 5
> +};
> +
> +#define LMK_PROCFS_NAME "lmkstats"
> +
> +#ifdef CONFIG_ANDROID_LOW_MEMORY_KILLER_STATS
> +void lmk_inc_stats(int key);
> +int __init init_procfs_lmk(void);
> +#else
> +static inline void lmk_inc_stats(int key) { return; };
> +static inline int __init init_procfs_lmk(void) { return 0; };
> +#endif
> -- 
> 2.4.2
> 
> 
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-- 
Michal Hocko
SUSE Labs