Re: [RFC PATCH] mm/workingset : judge file page activity via timestamp

[Zhaoyang Huang]

fix one mailbox and update for some information

Comparing to http://lkml.kernel.org/r/1554348617-12897-1-git-send-email-huangzhaoyang@xxxxxxxxx,
this commit fix the packing order error and add trace_printk for
reference debug information.

For johannes's comments, please find bellowing for my feedback.



On Wed, Apr 17, 2019 at 3:59 PM Zhaoyang Huang <huangzhaoyang@xxxxxxxxx> wrote:
>
> add Johannes and answer his previous question.
>
> @Johannes Weiner
> Yes. I do agree with you about the original thought of sacrificing
> long distance access pages when huge memory demands arise. The problem
> is what is the criteria of the distance, which you can find from what
> I comment in the patch, that is, some pages have long refault_distance
> while having a very short access time in between. I think the latter
> one should be take into consideration or as part of the finnal
> decision of if the page should be active/inactive.
>
> On Wed, Apr 17, 2019 at 3:48 PM Zhaoyang Huang <huangzhaoyang@xxxxxxxxx> wrote:
> >
> > From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
> >
> > This patch introduce timestamp into workingset's entry and judge if the page
> > is active or inactive via active_file/refault_ratio instead of refault distance.
> >
> > The original thought is coming from the logs we got from trace_printk in this
> > patch, we can find about 1/5 of the file pages' refault are under the
> > scenario[1],which will be counted as inactive as they have a long refault distance
> > in between access. However, we can also know from the time information that the
> > page refault quickly as comparing to the average refault time which is calculated
> > by the number of active file and refault ratio. We want to save these kinds of
> > pages from evicted earlier as it used to be. The refault ratio is the value
> > which can reflect lru's average file access frequency and also can be deemed as a
> > prediction of future.
> >
> > The patch is tested on an android system and reduce 30% of page faults, while
> > 60% of the pages remain the original status as (refault_distance < active_file)
> > indicates. Pages status got from ftrace during the test can refer to [2].
> >
> > [1]
> > system_server workingset_refault: WKST_ACT[0]:rft_dis 265976, act_file 34268 rft_ratio 3047 rft_time 0 avg_rft_time 11 refault 295592 eviction 29616 secs 97 pre_secs 97
> > HwBinder:922  workingset_refault: WKST_ACT[0]:rft_dis 264478, act_file 35037 rft_ratio 3070 rft_time 2 avg_rft_time 11 refault 310078 eviction 45600 secs 101 pre_secs 99
> >
> > [2]
> > WKST_ACT[0]:   original--INACTIVE  commit--ACTIVE
> > WKST_ACT[1]:   original--ACTIVE    commit--ACTIVE
> > WKST_INACT[0]: original--INACTIVE  commit--INACTIVE
> > WKST_INACT[1]: original--ACTIVE    commit--INACTIVE
> >
> > Signed-off-by: Zhaoyang Huang <huangzhaoyang@xxxxxxxxx>
> > ---
> >  include/linux/mmzone.h |   1 +
> >  mm/workingset.c        | 120 +++++++++++++++++++++++++++++++++++++++++++++----
> >  2 files changed, 112 insertions(+), 9 deletions(-)
> >
> > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> > index 32699b2..6f30673 100644
> > --- a/include/linux/mmzone.h
> > +++ b/include/linux/mmzone.h
> > @@ -240,6 +240,7 @@ struct lruvec {
> >         atomic_long_t                   inactive_age;
> >         /* Refaults at the time of last reclaim cycle */
> >         unsigned long                   refaults;
> > +       atomic_long_t                   refaults_ratio;
> >  #ifdef CONFIG_MEMCG
> >         struct pglist_data *pgdat;
> >  #endif
> > diff --git a/mm/workingset.c b/mm/workingset.c
> > index 40ee02c..66c177b 100644
> > --- a/mm/workingset.c
> > +++ b/mm/workingset.c
> > @@ -160,6 +160,21 @@
> >                          MEM_CGROUP_ID_SHIFT)
> >  #define EVICTION_MASK  (~0UL >> EVICTION_SHIFT)
> >
> > +#ifdef CONFIG_64BIT
> > +#define EVICTION_SECS_POS_SHIFT 20
> > +#define EVICTION_SECS_SHRINK_SHIFT 4
> > +#define EVICTION_SECS_POS_MASK  ((1UL << EVICTION_SECS_POS_SHIFT) - 1)
> > +#else
> > +#ifndef CONFIG_MEMCG
> > +#define EVICTION_SECS_POS_SHIFT 12
> > +#define EVICTION_SECS_SHRINK_SHIFT 4
> > +#define EVICTION_SECS_POS_MASK  ((1UL << EVICTION_SECS_POS_SHIFT) - 1)
> > +#else
> > +#define EVICTION_SECS_POS_SHIFT 0
> > +#define EVICTION_SECS_SHRINK_SHIFT 0
> > +#define NO_SECS_IN_WORKINGSET
> > +#endif
> > +#endif
> >  /*
> >   * Eviction timestamps need to be able to cover the full range of
> >   * actionable refaults. However, bits are tight in the radix tree
> > @@ -169,10 +184,54 @@
> >   * evictions into coarser buckets by shaving off lower timestamp bits.
> >   */
> >  static unsigned int bucket_order __read_mostly;
> > -
> > +#ifdef NO_SECS_IN_WORKINGSET
> > +static void pack_secs(unsigned long *peviction) { }
> > +static unsigned int unpack_secs(unsigned long entry) {return 0; }
> > +#else
> > +/*
> > + * Shrink the timestamp according to its value and store it together
> > + * with the shrink size in the entry.
> > + */
> > +static void pack_secs(unsigned long *peviction)
> > +{
> > +       unsigned int secs;
> > +       unsigned long eviction;
> > +       int order;
> > +       int secs_shrink_size;
> > +       struct timespec ts;
> > +
> > +       get_monotonic_boottime(&ts);
> > +       secs = (unsigned int)ts.tv_sec ? (unsigned int)ts.tv_sec : 1;
> > +       order = get_count_order(secs);
> > +       secs_shrink_size = (order <= EVICTION_SECS_POS_SHIFT)
> > +                       ? 0 : (order - EVICTION_SECS_POS_SHIFT);
> > +
> > +       eviction = *peviction;
> > +       eviction = (eviction << EVICTION_SECS_POS_SHIFT)
> > +                       | ((secs >> secs_shrink_size) & EVICTION_SECS_POS_MASK);
> > +       eviction = (eviction << EVICTION_SECS_SHRINK_SHIFT) | (secs_shrink_size & 0xf);
> > +       *peviction = eviction;
> > +}
> > +/*
> > + * Unpack the second from the entry and restore the value according to the
> > + * shrink size.
> > + */
> > +static unsigned int unpack_secs(unsigned long entry)
> > +{
> > +       unsigned int secs;
> > +       int secs_shrink_size;
> > +
> > +       secs_shrink_size = entry & ((1 << EVICTION_SECS_SHRINK_SHIFT) - 1);
> > +       entry >>= EVICTION_SECS_SHRINK_SHIFT;
> > +       secs = entry & EVICTION_SECS_POS_MASK;
> > +       secs = secs << secs_shrink_size;
> > +       return secs;
> > +}
> > +#endif
> >  static void *pack_shadow(int memcgid, pg_data_t *pgdat, unsigned long eviction)
> >  {
> >         eviction >>= bucket_order;
> > +       pack_secs(&eviction);
> >         eviction = (eviction << MEM_CGROUP_ID_SHIFT) | memcgid;
> >         eviction = (eviction << NODES_SHIFT) | pgdat->node_id;
> >         eviction = (eviction << RADIX_TREE_EXCEPTIONAL_SHIFT);
> > @@ -181,20 +240,24 @@ static void *pack_shadow(int memcgid, pg_data_t *pgdat, unsigned long eviction)
> >  }
> >
> >  static void unpack_shadow(void *shadow, int *memcgidp, pg_data_t **pgdat,
> > -                         unsigned long *evictionp)
> > +                         unsigned long *evictionp, unsigned int *prev_secs)
> >  {
> >         unsigned long entry = (unsigned long)shadow;
> >         int memcgid, nid;
> > +       unsigned int secs;
> >
> >         entry >>= RADIX_TREE_EXCEPTIONAL_SHIFT;
> >         nid = entry & ((1UL << NODES_SHIFT) - 1);
> >         entry >>= NODES_SHIFT;
> >         memcgid = entry & ((1UL << MEM_CGROUP_ID_SHIFT) - 1);
> >         entry >>= MEM_CGROUP_ID_SHIFT;
> > +       secs = unpack_secs(entry);
> > +       entry >>= (EVICTION_SECS_POS_SHIFT + EVICTION_SECS_SHRINK_SHIFT);
> >
> >         *memcgidp = memcgid;
> >         *pgdat = NODE_DATA(nid);
> >         *evictionp = entry << bucket_order;
> > +       *prev_secs = secs;
> >  }
> >
> >  /**
> > @@ -242,9 +305,22 @@ bool workingset_refault(void *shadow)
> >         unsigned long refault;
> >         struct pglist_data *pgdat;
> >         int memcgid;
> > +#ifndef NO_SECS_IN_WORKINGSET
> > +       unsigned long avg_refault_time;
> > +       unsigned long refault_time;
> > +       int tradition;
> > +       unsigned int prev_secs;
> > +       unsigned int secs;
> > +       unsigned long refaults_ratio;
> > +#endif
> > +       struct timespec ts;
> > +       /*
> > +       convert jiffies to second
> > +       */
> > +       get_monotonic_boottime(&ts);
> > +       secs = (unsigned int)ts.tv_sec ? (unsigned int)ts.tv_sec : 1;
> >
> > -       unpack_shadow(shadow, &memcgid, &pgdat, &eviction);
> > -
> > +       unpack_shadow(shadow, &memcgid, &pgdat, &eviction, &prev_secs);
> >         rcu_read_lock();
> >         /*
> >          * Look up the memcg associated with the stored ID. It might
> > @@ -288,14 +364,37 @@ 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) {
> > +#ifndef NO_SECS_IN_WORKINGSET
> > +       refaults_ratio = (atomic_long_read(&lruvec->inactive_age) + 1) / secs;
> > +       atomic_long_set(&lruvec->refaults_ratio, refaults_ratio);
> > +       refault_time = secs - prev_secs;
> > +       avg_refault_time = active_file / refaults_ratio;
> > +       tradition = !!(refault_distance < active_file);
> > +       if (refault_time <= avg_refault_time) {
> > +#else
> > +       if (refault_distance < active_file) {
> > +#endif
> >                 inc_lruvec_state(lruvec, WORKINGSET_ACTIVATE);
> > +#ifndef NO_SECS_IN_WORKINGSET
> > +               trace_printk("WKST_ACT[%d]:rft_dis %ld, act_file %ld \
> > +                               rft_ratio %ld rft_time %ld avg_rft_time %ld \
> > +                               refault %ld eviction %ld secs %d pre_secs %d\n",
> > +                               tradition, refault_distance, active_file,
> > +                               refaults_ratio, refault_time, avg_refault_time,
> > +                               refault, eviction, secs, prev_secs);
> > +#endif
> >                 rcu_read_unlock();
> >                 return true;
> >         }
> > +#ifndef NO_SECS_IN_WORKINGSET
> > +       trace_printk("WKST_INACT[%d]:rft_dis %ld, act_file %ld \
> > +                       rft_ratio %ld rft_time %ld avg_rft_time %ld \
> > +                       refault %ld eviction %ld secs %d pre_secs %d\n",
> > +                       tradition, refault_distance, active_file,
> > +                       refaults_ratio, refault_time, avg_refault_time,
> > +                       refault, eviction, secs, prev_secs);
> > +#endif
> >         rcu_read_unlock();
> >         return false;
> >  }
> > @@ -513,7 +612,9 @@ static int __init workingset_init(void)
> >         unsigned int max_order;
> >         int ret;
> >
> > -       BUILD_BUG_ON(BITS_PER_LONG < EVICTION_SHIFT);
> > +       BUILD_BUG_ON(BITS_PER_LONG < (EVICTION_SHIFT
> > +                               + EVICTION_SECS_POS_SHIFT
> > +                               + EVICTION_SECS_SHRINK_SHIFT));
> >         /*
> >          * Calculate the eviction bucket size to cover the longest
> >          * actionable refault distance, which is currently half of
> > @@ -521,7 +622,8 @@ 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_SECS_POS_SHIFT - EVICTION_SECS_SHRINK_SHIFT;
> >         max_order = fls_long(totalram_pages - 1);
> >         if (max_order > timestamp_bits)
> >                 bucket_order = max_order - timestamp_bits;
> > --
> > 1.9.1
> >