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Date: Sat, 6 Apr 2019 17:43:26 -0700
From: Suren Baghdasaryan <surenb@...gle.com>
To: Zhaoyang Huang <huangzhaoyang@...il.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Vlastimil Babka <vbabka@...e.cz>,
Pavel Tatashin <pasha.tatashin@...cle.com>,
Joonsoo Kim <iamjoonsoo.kim@....com>,
David Rientjes <rientjes@...gle.com>,
Roman Gushchin <guro@...com>, Jeff Layton <jlayton@...hat.com>,
Matthew Wilcox <mawilcox@...rosoft.com>,
linux-mm <linux-mm@...ck.org>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm:workingset use real time to judge activity of the file page
On Wed, Apr 3, 2019 at 7:03 PM Zhaoyang Huang <huangzhaoyang@...il.com> wrote:
>
> From: Zhaoyang Huang <Zhaoyang Huang@...soc.com>
>
> In previous implementation, the number of refault pages is used
> for judging the refault period of each page, which is not precised.
> We introduce the timestamp into the workingset's entry to measure
> the file page's activity.
>
> 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@...il.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;
I also wonder how many times the division above yields a 0...
> + refault_time = jiffies - prev_jiff;
> + avg_refault_time = refault_distance / lruvec->refaults_ratio;
and then used here as a denominator.
> + 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
>
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