Re: [PATCH] mm:workingset use real time to judge activity of the file page

[Michal Hocko <mhocko@kernel.org>]

[Fixup email for Pavel and add Johannes]

On Thu 04-04-19 11:30:17, Zhaoyang Huang wrote:
> From: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
> 
> In previous implementation, the number of refault pages is used
> for judging the refault period of each page, which is not precised as
> eviction of other files will be affect a lot on current cache.
> We introduce the timestamp into the workingset's entry and refault ratio
> to measure the file page's activity. It helps to decrease the affection
> of other files(average refault ratio can reflect the view of whole system
> 's memory).
> The patch is tested on an Android system, which can be described as
> comparing the launch time of an application between a huge memory
> consumption. The result is launch time decrease 50% and the page fault
> during the test decrease 80%.
> 
> Signed-off-by: Zhaoyang Huang <huangzhaoyang@gmail.com>
> ---
>  include/linux/mmzone.h |  2 ++
>  mm/workingset.c        | 24 +++++++++++++++++-------
>  2 files changed, 19 insertions(+), 7 deletions(-)
> 
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index 32699b2..c38ba0a 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -240,6 +240,8 @@ struct lruvec {
>  	atomic_long_t			inactive_age;
>  	/* Refaults at the time of last reclaim cycle */
>  	unsigned long			refaults;
> +	atomic_long_t			refaults_ratio;
> +	atomic_long_t			prev_fault;
>  #ifdef CONFIG_MEMCG
>  	struct pglist_data *pgdat;
>  #endif
> diff --git a/mm/workingset.c b/mm/workingset.c
> index 40ee02c..6361853 100644
> --- a/mm/workingset.c
> +++ b/mm/workingset.c
> @@ -159,7 +159,7 @@
>  			 NODES_SHIFT +	\
>  			 MEM_CGROUP_ID_SHIFT)
>  #define EVICTION_MASK	(~0UL >> EVICTION_SHIFT)
> -
> +#define EVICTION_JIFFIES (BITS_PER_LONG >> 3)
>  /*
>   * Eviction timestamps need to be able to cover the full range of
>   * actionable refaults. However, bits are tight in the radix tree
> @@ -175,18 +175,22 @@ static void *pack_shadow(int memcgid, pg_data_t *pgdat, unsigned long eviction)
>  	eviction >>= bucket_order;
>  	eviction = (eviction << MEM_CGROUP_ID_SHIFT) | memcgid;
>  	eviction = (eviction << NODES_SHIFT) | pgdat->node_id;
> +	eviction = (eviction << EVICTION_JIFFIES) | (jiffies >> EVICTION_JIFFIES);
>  	eviction = (eviction << RADIX_TREE_EXCEPTIONAL_SHIFT);
>  
>  	return (void *)(eviction | RADIX_TREE_EXCEPTIONAL_ENTRY);
>  }
>  
>  static void unpack_shadow(void *shadow, int *memcgidp, pg_data_t **pgdat,
> -			  unsigned long *evictionp)
> +			  unsigned long *evictionp, unsigned long *prev_jiffp)
>  {
>  	unsigned long entry = (unsigned long)shadow;
>  	int memcgid, nid;
> +	unsigned long prev_jiff;
>  
>  	entry >>= RADIX_TREE_EXCEPTIONAL_SHIFT;
> +	entry >>= EVICTION_JIFFIES;
> +	prev_jiff = (entry & ((1UL << EVICTION_JIFFIES) - 1)) << EVICTION_JIFFIES;
>  	nid = entry & ((1UL << NODES_SHIFT) - 1);
>  	entry >>= NODES_SHIFT;
>  	memcgid = entry & ((1UL << MEM_CGROUP_ID_SHIFT) - 1);
> @@ -195,6 +199,7 @@ static void unpack_shadow(void *shadow, int *memcgidp, pg_data_t **pgdat,
>  	*memcgidp = memcgid;
>  	*pgdat = NODE_DATA(nid);
>  	*evictionp = entry << bucket_order;
> +	*prev_jiffp = prev_jiff;
>  }
>  
>  /**
> @@ -242,8 +247,12 @@ bool workingset_refault(void *shadow)
>  	unsigned long refault;
>  	struct pglist_data *pgdat;
>  	int memcgid;
> +	unsigned long refault_ratio;
> +	unsigned long prev_jiff;
> +	unsigned long avg_refault_time;
> +	unsigned long refault_time;
>  
> -	unpack_shadow(shadow, &memcgid, &pgdat, &eviction);
> +	unpack_shadow(shadow, &memcgid, &pgdat, &eviction, &prev_jiff);
>  
>  	rcu_read_lock();
>  	/*
> @@ -288,10 +297,11 @@ bool workingset_refault(void *shadow)
>  	 * list is not a problem.
>  	 */
>  	refault_distance = (refault - eviction) & EVICTION_MASK;
> -
>  	inc_lruvec_state(lruvec, WORKINGSET_REFAULT);
> -
> -	if (refault_distance <= active_file) {
> +	lruvec->refaults_ratio = atomic_long_read(&lruvec->inactive_age) / jiffies;
> +	refault_time = jiffies - prev_jiff;
> +	avg_refault_time = refault_distance / lruvec->refaults_ratio;
> +	if (refault_time <= avg_refault_time) {
>  		inc_lruvec_state(lruvec, WORKINGSET_ACTIVATE);
>  		rcu_read_unlock();
>  		return true;
> @@ -521,7 +531,7 @@ static int __init workingset_init(void)
>  	 * some more pages at runtime, so keep working with up to
>  	 * double the initial memory by using totalram_pages as-is.
>  	 */
> -	timestamp_bits = BITS_PER_LONG - EVICTION_SHIFT;
> +	timestamp_bits = BITS_PER_LONG - EVICTION_SHIFT - EVICTION_JIFFIES;
>  	max_order = fls_long(totalram_pages - 1);
>  	if (max_order > timestamp_bits)
>  		bucket_order = max_order - timestamp_bits;
> -- 
> 1.9.1

-- 
Michal Hocko
SUSE Labs