Re: [RFC PATCH 0/2] mm: zsmalloc: make shrinker compaction budget-aware

[Sergey Senozhatsky <senozhatsky@chromium.org>]

Adding Chris for visibility

On (26/10/29 11:26), Sergey Senozhatsky wrote:
> On (26/08/07 09:25), Nhat Pham wrote:
> > Hmm we'd need to collect more data in our workloads to determine, but
> > if we can compute compactable ratio (freeable_pages / total_pages) on
> > a per size class basis, can we just skip the size class whose ratio is
> > too bad? Would that at least cut down on the vast majority of
> > fruitless memcpys and lock acquisitions etc?

[..]

> ---
> 
> diff --git a/mm/Kconfig b/mm/Kconfig
> index afff1b25b543..72542946bc53 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -157,6 +157,17 @@ config ZSMALLOC_CHAIN_SIZE
>  
>  	  For more information, see zsmalloc documentation.
>  
> +config ZSMALLOC_SHRINKER
> +	bool "Enable zsmalloc pool shrinker"
> +	default y
> +	help
> +	  This option enables the zsmalloc pool shrinker, which allows
> +	  the zsmalloc pool to be shrunk when the system is under memory
> +	  pressure. The shrinker will attempt to free up memory by
> +	  compacting zspages and releasing empty zspages back to the system.
> +
> +	  If unsure, say N.
> +
>  endmenu
>  
>  menu "Slab allocator options"
> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> index 7ef80e0da626..e0d7ab9142bb 100644
> --- a/mm/zsmalloc.c
> +++ b/mm/zsmalloc.c
> @@ -276,8 +276,10 @@ struct zs_pool {
>  
>  	struct zs_pool_stats stats;
>  
> +#ifdef CONFIG_ZSMALLOC_SHRINKER
>  	/* Compact classes */
>  	struct shrinker *shrinker;
> +#endif
>  
>  #ifdef CONFIG_ZSMALLOC_STAT
>  	struct dentry *stat_dentry;
> @@ -2050,8 +2052,9 @@ void zs_pool_stats(struct zs_pool *pool, struct zs_pool_stats *stats)
>  }
>  EXPORT_SYMBOL_GPL(zs_pool_stats);
>  
> +#ifdef CONFIG_ZSMALLOC_SHRINKER
>  static unsigned long zs_shrinker_scan(struct shrinker *shrinker,
> -		struct shrink_control *sc)
> +				      struct shrink_control *sc)
>  {
>  	unsigned long pages_freed;
>  	struct zs_pool *pool = shrinker->private_data;
> @@ -2067,7 +2070,7 @@ static unsigned long zs_shrinker_scan(struct shrinker *shrinker,
>  }
>  
>  static unsigned long zs_shrinker_count(struct shrinker *shrinker,
> -		struct shrink_control *sc)
> +				       struct shrink_control *sc)
>  {
>  	int i;
>  	struct size_class *class;
> @@ -2105,6 +2108,10 @@ static int zs_register_shrinker(struct zs_pool *pool)
>  
>  	return 0;
>  }
> +#else
> +static void zs_unregister_shrinker(struct zs_pool *pool) { }
> +static int zs_register_shrinker(struct zs_pool *pool) { return 0; }
> +#endif
>  
>  static int calculate_zspage_chain_size(int class_size)
>  {